Journal articles: 'C1 Complex'

1

Guiot, Bernard, and Richard G. Fessler. "Complex atlantoaxial fractures." Journal of Neurosurgery: Spine 91, no. 2 (October 1999): 139–43. http://dx.doi.org/10.3171/spi.1999.91.2.0139.

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Object. The authors conducted a retrospective study to evaluate the treatment of complex C1–2 fractures. Methods. There were 10 cases of complex C1–2 fractures. Six patients were men (median age 58 years) and four patients were women (median age 55.5 years). Injuries resulted from seven falls, two motor vehicle accidents, and one diving incident. Three patients suffered from upper-extremity weakness. Neurological function in seven patients was intact preoperatively. Fracture combinations included six Jefferson/Type II odontoid, two anterior ring/Type II odontoid, one posterior ring/Type II odontoid, and one posterior ring/Type III odontoid/Type III hangman's fracture. All patients underwent surgery, five after halo immobilization for an average of 4 months failed to provide stability. Treatment included placement of six odontoid screws, one posterior C1–2 transarticular screw, one odontoid screw with anterior C1–2 transarticular screw fixation, one C1–2 transarticular screw with C1–2 Songer cable fusion, and one odontoid screw with bilateral C-2 pedicle screw fixation. Specific treatment was determined by the combination of fractures. Postoperatively, all patients were immobilized in a hard collar for 3 months. There were no intraoperative surgery-related complications. The mean follow-up period was 28.5 months. Neurological recovery was observed in one of three patients who presented with neurological deficits. Fusion occurred in all cases. Conclusions. The goals in treating these complex fractures are to achieve early maximum stability and minimum reduction in range of motion. These are often competing phenomena. Frequently in cases of atlas—axis fracture, odontoid screw fixation combined with hard collar immobilization is the best therapy, provided the transverse atlantal ligament is competent. If not, C1–2 stabilization with placement of transarticular screws is required for best results.

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2

Colomb, Maurice, and Gérard Arlaud. "C1 complex of human complement." Journal of Molecular Biology 195, no. 2 (May 1987): 435. http://dx.doi.org/10.1016/0022-2836(87)90662-0.

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3

Mortensen, Simon A., Bjørn Sander, Rasmus K. Jensen, Jan S. Pedersen, Monika M. Golas, Steffen Thiel, and Gregers R. Andersen. "Models of the complement C1 complex." Proceedings of the National Academy of Sciences 115, no. 17 (April 13, 2018): E3866. http://dx.doi.org/10.1073/pnas.1803577115.

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4

Weiss, V., and J. Engel. "Functional models of the C1 complex." Journal of Molecular Biology 195, no. 2 (May 1987): 437–38. http://dx.doi.org/10.1016/0022-2836(87)90663-2.

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5

Levine, Alan M., Jeffrey Fischgrund, and Charles Edwards. "Fractures of the C1–2 Complex." Journal of Orthopaedic Trauma 7, no. 2 (April 1993): 172. http://dx.doi.org/10.1097/00005131-199304000-00053.

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6

Vilela, Marcelo D., Charles Jermani, and Bruno P. Braga. "C1 lateral mass screws for posterior segmental stabilization of the upper cervical spine and a new method of three-point rigid fixation of the C1-C2 complex." Arquivos de Neuro-Psiquiatria 64, no. 3b (September 2006): 762–67. http://dx.doi.org/10.1590/s0004-282x2006000500012.

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OBJECTIVE: To describe our experience with C1 lateral mass screws as part of a construct for C1-2 stabilization and report an alternate method of C1-C2 complex three-point fixation. METHOD: All patients that had at least one screw placed in the lateral mass of C1 as part of a construct for stabilization of the C1-C2 complex entered this study. In selected patients who had a higher chance of nonunion an alternate construct was used: transarticular C1-C2 screws combined with C1 lateral mass screws. RESULTS: Twenty-one C1 lateral mass screws were placed in 11 patients. In three patients the alternate construct was used. All patients had a demonstrable solid and stable fusion on follow-up. CONCLUSION: C1 lateral mass screws are safe and provide immediate stability. The use of C1-C2 transarticular screws combined with C1 lateral mass screws is a feasible and also an excellent alternative for a three-point fixation of the C1-C2 complex.

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7

GOEL, VIJAY K., JOHN M. WINTERBOTTOM, KARYR SCHULTE, HAN CHANG, LARS G. GILBERTSON, ARTHUR G. PUDGIL, and JONG K. GWON. "Ligamentous Laxity Across C0-C1-C2 Complex." SPINE 15, no. 10 (October 1990): 990–96. http://dx.doi.org/10.1097/00007632-199010000-00002.

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8

GOEL, VIJAY K., JOHN M. WINTERBOTTOM, KARYR SCHULTE, HAN CHANG, LARS G. GILBERTSON, ARTHUR G. PUDGIL, and JONG K. GWON. "Ligamentous Laxity Across C0-C1-C2 Complex." SPINE 15, no. 10 (October 1990): 990–96. http://dx.doi.org/10.1097/00007632-199015100-00002.

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9

Arlaud, Gérard J., Christine Gaboriaud, Wai Li Ling, and Nicole M. Thielens. "Structure of the C1 complex of complement." Proceedings of the National Academy of Sciences 114, no. 29 (July 12, 2017): E5766—E5767. http://dx.doi.org/10.1073/pnas.1703977114.

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10

ARLAUD, GÉRARD J., NICOLE M. THIELENS, and CHANTAL ILLY. "Arrangement of the C1 complex of complement." Biochemical Society Transactions 18, no. 6 (December 1, 1990): 1148–51. http://dx.doi.org/10.1042/bst0181148.

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11

Mortensen, Simon A., Bjoern Sander, Rasmus K. Jensen, Jan Skov Pedersen, Monika M. Golas, Jens C. Jensenius, Annette G. Hansen, Steffen Thiel, and Gregers R. Andersen. "Structure and activation of C1, the complex initiating the classical pathway of the complement cascade." Proceedings of the National Academy of Sciences 114, no. 5 (January 19, 2017): 986–91. http://dx.doi.org/10.1073/pnas.1616998114.

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The complement system is an important antimicrobial and inflammation-generating component of the innate immune system. The classical pathway of complement is activated upon binding of the 774-kDa C1 complex, consisting of the recognition molecule C1q and the tetrameric protease complex C1r2s2, to a variety of activators presenting specific molecular patterns such as IgG- and IgM-containing immune complexes. A canonical model entails a C1r2s2with its serine protease domains tightly packed together in the center of C1 and an intricate intramolecular reaction mechanism for activation of C1r and C1s, induced upon C1 binding to the activator. Here, we show that the serine protease domains of C1r and C1s are located at the periphery of the C1r2s2tetramer both when alone or within the nonactivated C1 complex. Our structural studies indicate that the C1 complex adopts a conformation incompatible with intramolecular activation of C1, suggesting instead that intermolecular proteolytic activation between neighboring C1 complexes bound to a complement activating surface occurs. Our results rationalize how a multitude of structurally unrelated molecular patterns can activate C1 and suggests a conserved mechanism for complement activation through the classical and the related lectin pathway.

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12

Laurell, A. B., U. Mårtensson, and A. G. Sjöholm. "C1 dissociation. Spontaneous generation in human serum of a trimer complex containing C1 inactivator, activated C1r, and zymogen C1s." Journal of Immunology 139, no. 12 (December 15, 1987): 4145–51. http://dx.doi.org/10.4049/jimmunol.139.12.4145.

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Abstract Activation of the C1 complex in the presence of C1 inactivator (C1 IA) is known to result in the formation of tetramer C1 IA-C1r-C1s-C1 IA complexes that are dissociated from C1q. Both C1r and C1s of the tetramers are present in their activated forms. The present investigation concerned the generation of trimer complexes containing C1 IA, activated C1r, and zymogen C1s (C1 IA-C1r-C1s). C1 IA-C1r-C1s were released from C1q and were formed in high concentration during prolonged incubation (1 to 3 days) of normal serum at 37 degrees C without addition of activators. By contrast, dissociation of C1 with formation of C1 IA-C1r-C1s-C1 IA was complete within 30 min at 37 degrees C, when the serum was treated with heat-aggregated IgG (1 g/liter). On size exclusion chromatography (TSK-4000), C1 IA-C1r-C1s and C1 IA-C1r-C1s-C1 IA emerged with apparent m.w. of 320,000 and 460,000, respectively. The composition of the complexes was examined by absorption of serum with F(ab')2 anti-C1s- or anti-C1r-coated Sepharose beads. Eluates were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis combined with immunoblotting. Under nonreducing conditions, heat-aggregated IgG-treated serum showed high concentrations of C1 IA-C1r (m.w. 202,000) and C1 IA-C1s (m.w. 194,000), while serum incubated at 37 degrees C without activators showed high concentrations of C1 IA-C1r but no C1 IA-C1s. Under reducing conditions, heat-aggregated IgG-treated serum showed m.w. 120,000 and 110,000 complexes of C1 IA and the C1r and C1s light chains, respectively. Uncleaved C1s and the m.w. 120,000 complex was found in serum that was incubated at 37 degrees C without activators. Consistent with results obtained by size exclusion chromatography, analysis by crossed immunoelectrophoresis and by electroimmunoassay showed that C1s could be released from C1 IA-C1r-C1s in the presence of EDTA.

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13

Verbitsky, Misha. "Quaternionic Dolbeault complex and vanishing theorems on hyperkähler manifolds." Compositio Mathematica 143, no. 6 (November 2007): 1576–92. http://dx.doi.org/10.1112/s0010437x07002746.

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AbstractLet (M,I,J,K) be a compact hyperkähler manifold, $\dim _{\mathbb {H}}M=n$, and L a non-trivial holomorphic line bundle on (M,I). Using the quaternionic Dolbeault complex, we prove the following vanishing theorem for holomorphic cohomology of L. If c1(L) lies in the closure $\hat K$ of the dual Kähler cone, then Hi(L)=0 for i>n. If c1(L) lies in the opposite cone $-\hat K$, then Hi(L)=0 for i<n. Finally, if c1(L) is neither in $\hat K$ nor in $-\hat K$, then Hi(L)=0 for $i\neq n$.

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14

Patston, PA, RL Medcalf, Y. Kourteva, and M. Schapira. "C1-inhibitor-serine proteinase complexes and the biosynthesis of C1- inhibitor by Hep G2 and U 937 cells." Blood 82, no. 11 (December 1, 1993): 3371–79. http://dx.doi.org/10.1182/blood.v82.11.3371.3371.

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Abstract The biosynthesis of the serpin alpha 1-proteinase inhibitor is regulated by a feedback mechanism whereby complexes between alpha 1- proteinase inhibitor and serine proteinases bind to liver cells and monocytes, a reaction that activates alpha 1-proteinase-inhibitor gene transcription. Such a mechanism may form the basis for the development of new therapeutic strategies for serpin deficiency states with reduced levels of otherwise normally functioning serpins. This issue was addressed for C1-inhibitor, the missing serpin in hereditary angioedema. C1-inhibitor biosynthesis by Hep G2 hepatoma cells was assessed by enzyme-linked immunosorbant assay, by metabolic labeling followed by immunoprecipitation, and by Northern blotting. C1-inhibitor biosynthesis was stimulated by gamma-interferon (100 U/mL) but not by cell exposure to C1-inhibitor-kallikrein (1 mumol/L), C1-inhibitor-C1s (1 mumol/L), and C1-inhibitor-plasmin complexes (1 mumol/L) or to reactive site-cleaved C1-inhibitor (1 mumol/L). Moreover, radioiodinated C1s-C1-inhibitor complex did not bind to Hep G2 cells. C1-inhibitor-kallikrein complex was also without effect on C1-inhibitor mRNA in U 937 cells. Therefore, the proposed mechanism, by which serpin- enzyme complex or reactive site-cleaved serpin binding to a specific receptor provides a signal for the stimulation of the biosynthesis of that serpin, is not operative for the biosynthesis of C1-inhibitor by Hep G2 or U 937 cells.

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15

Patston, PA, RL Medcalf, Y. Kourteva, and M. Schapira. "C1-inhibitor-serine proteinase complexes and the biosynthesis of C1- inhibitor by Hep G2 and U 937 cells." Blood 82, no. 11 (December 1, 1993): 3371–79. http://dx.doi.org/10.1182/blood.v82.11.3371.bloodjournal82113371.

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The biosynthesis of the serpin alpha 1-proteinase inhibitor is regulated by a feedback mechanism whereby complexes between alpha 1- proteinase inhibitor and serine proteinases bind to liver cells and monocytes, a reaction that activates alpha 1-proteinase-inhibitor gene transcription. Such a mechanism may form the basis for the development of new therapeutic strategies for serpin deficiency states with reduced levels of otherwise normally functioning serpins. This issue was addressed for C1-inhibitor, the missing serpin in hereditary angioedema. C1-inhibitor biosynthesis by Hep G2 hepatoma cells was assessed by enzyme-linked immunosorbant assay, by metabolic labeling followed by immunoprecipitation, and by Northern blotting. C1-inhibitor biosynthesis was stimulated by gamma-interferon (100 U/mL) but not by cell exposure to C1-inhibitor-kallikrein (1 mumol/L), C1-inhibitor-C1s (1 mumol/L), and C1-inhibitor-plasmin complexes (1 mumol/L) or to reactive site-cleaved C1-inhibitor (1 mumol/L). Moreover, radioiodinated C1s-C1-inhibitor complex did not bind to Hep G2 cells. C1-inhibitor-kallikrein complex was also without effect on C1-inhibitor mRNA in U 937 cells. Therefore, the proposed mechanism, by which serpin- enzyme complex or reactive site-cleaved serpin binding to a specific receptor provides a signal for the stimulation of the biosynthesis of that serpin, is not operative for the biosynthesis of C1-inhibitor by Hep G2 or U 937 cells.

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16

Koda, Shin-ichi, and Shinji Saito. "Multimeric structure enables the acceleration of KaiB-KaiC complex formation induced by ADP/ATP exchange inhibition." PLOS Computational Biology 18, no. 3 (March 7, 2022): e1009243. http://dx.doi.org/10.1371/journal.pcbi.1009243.

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Circadian clocks tick a rhythm with a nearly 24-hour period in a variety of organisms. In the clock proteins of cyanobacteria, KaiA, KaiB, and KaiC, known as a minimum circadian clock, the slow KaiB-KaiC complex formation is essential in determining the clock period. This complex formation, occurring when the C1 domain of KaiC hexamer binds ADP molecules produced by the ATPase activity of C1, is considered to be promoted by accumulating ADP molecules in C1 through inhibiting the ADP/ATP exchange (ADP release) rather than activating the ATP hydrolysis (ADP production). Significantly, this ADP/ATP exchange inhibition accelerates the complex formation together with its promotion, implying a potential role in the period robustness under environmental perturbations. However, the molecular mechanism of this simultaneous promotion and acceleration remains elusive because inhibition of a backward process generally slows down the whole process. In this article, to investigate the mechanism, we build several reaction models of the complex formation with the pre-binding process concerning the ATPase activity. In these models, six KaiB monomers cooperatively and rapidly bind to C1 when C1 binds ADP molecules more than a given threshold while stabilizing the binding-competent conformation of C1. Through comparison among the models proposed here, we then extract three requirements for the simultaneous promotion and acceleration: the stabilization of the binding-competent C1 by KaiB binding, slow ADP/ATP exchange in the binding-competent C1, and relatively fast ADP/ATP exchange occurring in the binding-incompetent C1 in the presence of KaiB. The last two requirements oblige KaiC to form a multimer. Moreover, as a natural consequence, the present models can also explain why the binding of KaiB to C1 reduces the ATPase activity of C1.

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17

Tseng, Y., P. Zavodszky, and V. N. Schumaker. "The human complement C1 complex has a picomolar dissociation constant at room temperature." Journal of Immunology 158, no. 2 (January 15, 1997): 937–44. http://dx.doi.org/10.4049/jimmunol.158.2.937.

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Abstract Periodic sampling of serum or reconstituted C1 initially diluted 1/2000 and 1/4000 (that is, to 0.1 and 0.05 nM) into a recombinant C1s-containing solution showed a gradual decline of hemolytic activity until equilibrium was approached, consistent with a simple dissociation, reassociation equilibrium, presumably C1 <--> C1q + C1r2C1s2. The presence of excess (5 nM) recombinant C1s minimized further dissociation of the C1r2C1s2, allowing the first step to be studied independently of the dissociation of C1r2C1s2 <--> C1r2 + 2 C1s. Reassociation experiments were also performed, starting with the dissociated C1 diluted to the same concentrations and following the regain of hemolytic activity to approximately the same values, showing that the same equilibrium had been achieved from both directions. Analysis of the kinetic data yielded forward and reverse rate constants and the equilibrium constant, for which values of approximately 72 and 3 pM were estimated at 0 and 23 degrees C, respectively. The effects of temperature, ionic strength, Ca2+ ion concentration, and activation of the zymogen on the equilibrium constants were explored; extreme sensitivity to temperature, ionic strength, and activation were found. At 23 and 30 degrees C, slow activation of C1 was also evident. Highly purified, reconstituted C1 yielded approximately the same values for the kinetic and equilibrium parameters as serum C1, suggesting that the structure of the reconstituted complex was similar to or identical with that of the serum C1 complex.

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18

Kaplan, AP, B. Gruber, and PC Harpel. "Assessment of Hageman factor activation in human plasma: quantification of activated Hageman factor-C1 inactivator complexes by an enzyme- linked differential antibody immunosorbent assay." Blood 66, no. 3 (September 1, 1985): 636–41. http://dx.doi.org/10.1182/blood.v66.3.636.bloodjournal663636.

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An enzyme-linked immunosorbent assay has been developed for the quantitation of activated Hageman factor-C1 inactivator (HF-C1 INH) complexes. Addition of increasing quantities of either of the major forms of activated Hageman factor (HFa or HFf) to normal plasma or to Hageman factor-deficient plasma leads to a dose-dependent increase in activated HF-C1 INH complexes. As little as 0.5 micrograms/mL of activated HF added to plasma can be detected, corresponding to activation of approximately 2% of plasma HF. The sensitivity of the assay is increased at least tenfold when complexes are formed in HF- deficient plasma, indicating competition between unactivated HF and activated HF-C1 INH complexes for binding to the antibody. Specificity is demonstrated in that addition of activated HF to hereditary angioedema plasma yields less than 1% of the activated HF-C1 INH complex formation obtained with normal plasma. Kaolin activation of HF- deficient plasma yields no detectable complex formation. Kaolin activation of prekallikrein-deficient plasma demonstrates a time- dependent increase in formation of activated HF-C1 INH complex consistent with the ability of HF in this plasma to autoactivate as the time of incubation with the surface is increased. Kaolin treatment of high-molecular weight (HMW) kininogen-deficient plasma yields an even more profound abnormality in the rate of formation of activated HF-C1 INH complexes reflecting the complex role of HMW kininogen in the initiation of contact activation. Although addition of corn inhibitor to plasma prevents activated HF-C1 INH complex formation, it does not inhibit activated HF sufficiently fast to prevent prekallikrein activation.

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19

Mishmar, Dan, and Moran Gershoni. "Treating speciation processes as complex traits." Nature Reviews Genetics 8, no. 4 (April 2007): 320. http://dx.doi.org/10.1038/nrg1968-c1.

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20

BẮnicẮ, Constantin, and Mihai Putinar. "On complex vector bundles on rational threefolds." Mathematical Proceedings of the Cambridge Philosophical Society 97, no. 2 (March 1985): 279–88. http://dx.doi.org/10.1017/s0305004100062824.

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It is known [14] that every topological complex vector bundle on a smooth rational surface admits an algebraic structure. In [10] one constructs algebraic vector bundles of rank 2 on with arbitrary Chern classes c1, c2 subject to the necessary topological condition c1 c2 = 0 (mod 2). However, in dimensions greater than 2 the Chern classes don't determine the topological type of a vector bundle. In [2] one classifies the topological complex vector bundles of rank 2 on and one proves that any such bundle admits an algebraic structure.

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21

Levine, Alan M., and Charles C. Edwards. "Treatment of Injuries in the C1-C2 Complex." Orthopedic Clinics of North America 17, no. 1 (January 1986): 31–44. http://dx.doi.org/10.1016/s0030-5898(20)30416-8.

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22

Arlaud, Gérard J., Maurice G. Colomb, and Jean Gagnon. "A functional model of the human C1 complex." Immunology Today 8, no. 4 (January 1987): 106–11. http://dx.doi.org/10.1016/0167-5699(87)90860-7.

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23

Mummaneni, Praveen V., Regis W. Haid, Amory J. Fiore, and Gerald E. Rodts. "Posterior Fixation Options for the C1-C2 Complex." Contemporary Neurosurgery 25, no. 1 (January 2003): 1–8. http://dx.doi.org/10.1097/00029679-200301150-00001.

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24

Marvaud, J. C., D. Hauser, M. Gibert, P. Boquet, M. W. Eklund, and M. R. Popoff. "Genetic organization of the botulinum neurotoxin complex C1." Toxicon 34, no. 10 (October 1996): 1091–92. http://dx.doi.org/10.1016/0041-0101(96)83823-2.

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25

Majumder, Rinku, Mary Ann Quinn-Allen, William H. Kane, and Barry R. Lentz. "A phosphatidylserine binding site in factor Va C1 domain regulates both assembly and activity of the prothrombinase complex." Blood 112, no. 7 (October 1, 2008): 2795–802. http://dx.doi.org/10.1182/blood-2008-02-138941.

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Abstract Tightly associated factor Va (FVa) and factor Xa (FXa) serve as the essential prothrombin-activating complex that assembles on phosphatidylserine (PS)–containing platelet membranes during blood coagulation. We have previously shown that (1) a soluble form of PS (C6PS) triggers assembly of a fully active FVa-FXa complex in solution and (2) that 2 molecules of C6PS bind to FVa light chain with one occupying a site in the C2 domain. We expressed human factor Va (rFVa) with mutations in either the C1 domain (Y1956,L1957)A, the C2 domain (W2063,W2064)A, or both C domains (Y1956,L1957,W2063,W2064)A. Mutations in the C1 and C1-C2 domains of rFVa reduced the rate of activation of prothrombin to thrombin by FXa in the presence of 400 μM C6PS by 14 000- to 15 000-fold relative to either wild-type or C2 mutant factor rFVa. The Kd's of FXa binding with rFVa (wild-type, C2 mutant, C1 mutant, and C1-C2 mutant) were 3, 4, 564, and 624 nM, respectively. Equilibrium dialysis experiments detected binding of 4, 3, and 2 molecules of C6PS to wild-type rFVa, C1-mutated, and C1,C2-mutated rFVa, respectively. Because FVa heavy chain binds 2 molecules of C6PS, we conclude that both C2 and C1 domains bind one C6PS, with binding to the C1 domain regulating prothrombinase complex assembly.

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26

Yang, Qian, Xin Cheng, YeXin Wang, BingWu Wang, ZheMing Wang, and Song Gao. "Two-step magnetic switching in a mononuclear iron(ii) complex around room temperature." Dalton Transactions 44, no. 19 (2015): 8938–41. http://dx.doi.org/10.1039/c5dt00585j.

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27

Kaplan, AP, B. Gruber, and PC Harpel. "Assessment of Hageman factor activation in human plasma: quantification of activated Hageman factor-C1 inactivator complexes by an enzyme- linked differential antibody immunosorbent assay." Blood 66, no. 3 (September 1, 1985): 636–41. http://dx.doi.org/10.1182/blood.v66.3.636.636.

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Abstract An enzyme-linked immunosorbent assay has been developed for the quantitation of activated Hageman factor-C1 inactivator (HF-C1 INH) complexes. Addition of increasing quantities of either of the major forms of activated Hageman factor (HFa or HFf) to normal plasma or to Hageman factor-deficient plasma leads to a dose-dependent increase in activated HF-C1 INH complexes. As little as 0.5 micrograms/mL of activated HF added to plasma can be detected, corresponding to activation of approximately 2% of plasma HF. The sensitivity of the assay is increased at least tenfold when complexes are formed in HF- deficient plasma, indicating competition between unactivated HF and activated HF-C1 INH complexes for binding to the antibody. Specificity is demonstrated in that addition of activated HF to hereditary angioedema plasma yields less than 1% of the activated HF-C1 INH complex formation obtained with normal plasma. Kaolin activation of HF- deficient plasma yields no detectable complex formation. Kaolin activation of prekallikrein-deficient plasma demonstrates a time- dependent increase in formation of activated HF-C1 INH complex consistent with the ability of HF in this plasma to autoactivate as the time of incubation with the surface is increased. Kaolin treatment of high-molecular weight (HMW) kininogen-deficient plasma yields an even more profound abnormality in the rate of formation of activated HF-C1 INH complexes reflecting the complex role of HMW kininogen in the initiation of contact activation. Although addition of corn inhibitor to plasma prevents activated HF-C1 INH complex formation, it does not inhibit activated HF sufficiently fast to prevent prekallikrein activation.

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28

Donaldson, VH, CJ Wagner, B. Tsuei, G. Kindness, DH Bing, RA Harrison, and FS Rosen. "Interactions of plasma kallikrein and C1-s with normal and dysfunctional C1(-)-inhibitor proteins from patients with hereditary angioneurotic edema: analytic gel studies." Blood 69, no. 4 (April 1, 1987): 1096–101. http://dx.doi.org/10.1182/blood.v69.4.1096.1096.

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Abstract Purified preparations of normal C1(-)-inhibitor (C1(-)-INH) formed high mol wt complexes with plasma kallikrein that were stable during sodium dodecyl sulfate (SDS)-gel electrophoresis, but most of the dysfunctional C1(-)-INH proteins isolated from plasma of patients with type II hereditary angioneurotic edema (HANE) did not. Two of eight dysfunctional C1(-)-INH proteins were cleaved to lower mol wt forms that were not seen following the reaction of normal C1(-)-INH with equimolar amounts, or less, of plasma kallikrein. Only the higher mol wt component of normal C1(-)-INH (106,000 mol wt) appeared to form a stable complex with the plasma kallikrein, whereas both the 106,000 and 96,000 mol wt forms made stable complexes with C1-s. When a preparation of normal C1(-)-INH containing a homogeneous single band of C1(-)-INH was exposed to C1-s or kallikrein, a “doublet” form evolved in which the heaviest band was in the original position of native C1(-)-INH; C1- s cleavage provided a second band of 96,000; and cleavage by kallikrein, a second band of 94,000 mol wt. We conclude that dysfunctional C1(-)-INH proteins from plasma of persons with type II hereditary angioneurotic edema have impaired interactions with plasma kallikrein and are heterogeneous with respect to these interactions. Moreover, the requirements for the formation of stable complexes between normal C1(-)-INH and plasma kallikrein differed from those for stable complex formation with C1-s. The doublet form of C1(-)-INH, which purified preparations frequently demonstrate, may be due to prior cleavage by C1-s or kallikrein.

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29

Donaldson, VH, CJ Wagner, B. Tsuei, G. Kindness, DH Bing, RA Harrison, and FS Rosen. "Interactions of plasma kallikrein and C1-s with normal and dysfunctional C1(-)-inhibitor proteins from patients with hereditary angioneurotic edema: analytic gel studies." Blood 69, no. 4 (April 1, 1987): 1096–101. http://dx.doi.org/10.1182/blood.v69.4.1096.bloodjournal6941096.

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Purified preparations of normal C1(-)-inhibitor (C1(-)-INH) formed high mol wt complexes with plasma kallikrein that were stable during sodium dodecyl sulfate (SDS)-gel electrophoresis, but most of the dysfunctional C1(-)-INH proteins isolated from plasma of patients with type II hereditary angioneurotic edema (HANE) did not. Two of eight dysfunctional C1(-)-INH proteins were cleaved to lower mol wt forms that were not seen following the reaction of normal C1(-)-INH with equimolar amounts, or less, of plasma kallikrein. Only the higher mol wt component of normal C1(-)-INH (106,000 mol wt) appeared to form a stable complex with the plasma kallikrein, whereas both the 106,000 and 96,000 mol wt forms made stable complexes with C1-s. When a preparation of normal C1(-)-INH containing a homogeneous single band of C1(-)-INH was exposed to C1-s or kallikrein, a “doublet” form evolved in which the heaviest band was in the original position of native C1(-)-INH; C1- s cleavage provided a second band of 96,000; and cleavage by kallikrein, a second band of 94,000 mol wt. We conclude that dysfunctional C1(-)-INH proteins from plasma of persons with type II hereditary angioneurotic edema have impaired interactions with plasma kallikrein and are heterogeneous with respect to these interactions. Moreover, the requirements for the formation of stable complexes between normal C1(-)-INH and plasma kallikrein differed from those for stable complex formation with C1-s. The doublet form of C1(-)-INH, which purified preparations frequently demonstrate, may be due to prior cleavage by C1-s or kallikrein.

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Cheng, Zheng Zai, Yu Jing Nie, Xiao Chao Yan, Rui Lei, and Su Su Lin. "Ethylene Polymerization by a New Zirconium Complex." Advanced Materials Research 214 (February 2011): 699–703. http://dx.doi.org/10.4028/www.scientific.net/amr.214.699.

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Novel zirconium complex C2 has been prepared by treatment of the ligand complex C1 with ZrCl4•2THF in dichloromethane solution. The complex C1 and C2 were characterized by 1H-NMR and IR. Activated by MAO, Complex C2 displays very high activity for ethylene polymerization under the reaction temperature of 30～80°C and the viscosity-average molecular weight of polyethylene is more than 3.50×104 when reaction temperature is no more than 60°C.The molecular-weight distribution measured by gel permeation reached 2.3.High melting points measured by DSC indicates that the polyethylene produced by complex C2 is high linearity and high crystallinity.

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Faulmann, E. L., M. Young, and M. D. Boyle. "Inactivation of the proteolytic activity of mouse nerve growth factor by human C1(activated)-inhibitor." Journal of Immunology 138, no. 12 (June 15, 1987): 4336–40. http://dx.doi.org/10.4049/jimmunol.138.12.4336.

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Abstract The interaction between the serine protease gamma subunit of NGF (gamma-NGF) and human C1(activated)-inhibitor (C1-Inh) has been studied. C1-Inh inactivates the protease activity of gamma-NGF as measured by its ability to cleave the synthetic substrate benzoyl-arginine-p-nitroanilide (L-BAPNA). Experiments in which gamma-NGF and C1-Inh were mixed at differing molar ratios indicated that inhibition was due to the formation of a 1:1 stoichiometric complex. Analysis of the interaction of 125I-labeled gamma-NGF with C1-Inh by SDS-PAGE and autoradiography indicated that a covalent bond was formed between gamma-NGF and C1-Inh. The covalent bond was hydrolyzed by hydroxylamine, which suggested that the two proteins were linked via an acyl linkage. The formation of this complex was time dependent and required the proteolytic activity of the gamma-NGF.

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Leek, E. Charles, and Stephen J. Johnston. "Functional specialization in the supplementary motor complex." Nature Reviews Neuroscience 10, no. 1 (January 2009): 78. http://dx.doi.org/10.1038/nrn2478-c1.

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Kovacsovics, T. J., M. C. Peitsch, A. Kress, and H. Isliker. "Antibody-independent activation of C1. I. Differences in the mechanism of C1 activation by nonimmune activators and by immune complexes: C1r-independent activation of C1s by cardiolipin vesicles." Journal of Immunology 138, no. 6 (March 15, 1987): 1864–70. http://dx.doi.org/10.4049/jimmunol.138.6.1864.

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Abstract C1 activation is controlled by the regulatory protein C1-inhibitor (C1-INH). In contrast to immune-complex-induced activation, which is insensitive to C1-INH, antibody-independent activation of C1 is modulated by C1-INH. The mechanisms regulating nonimmune activation were studied with two phospholipids varying in their capacity to activate C1 in the presence of C1-INH: cardiolipin (CL) and phosphatidylglycerol (PG). Whereas C1-INH consistently suppressed activation by PG vesicles, a dose-dependent increase in C1 activation was measured with CL vesicles above 40 mole %. A similar dose-response binding of C1s requiring C1q, but not C1r, was detected only on CL vesicles, but neither on PG vesicles nor on immune complexes. This binding was Ca2+-dependent, suggesting that dimeric C1s is involved and was inhibited by spermine. The C1q-bound C1s was specifically cleaved at 37 degrees C into its active 58 kDa and 28 kDa chains, in the absence of C1r. On the addition of anti-CL antibodies, the C1q-mediated cleavage of C1s by CL vesicles was specifically inhibited. The cleavage of C1r on CL vesicles was also determined. When macromolecular C1 was offered in the presence of C1-INH, C1r cleavage was detected; however, the presence of C1s was a critical factor for C1r activation, because it was required on CL vesicles, but not on immune complexes. These results show that nonimmune activation of C1 presents specific features which distinguish it from immune complex-induced activation. These characteristics varied with the capacity of antibody-independent activators to activate C1 in the presence of C1-INH.

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Lapczak, Jéssica Cristina de Oliveira, Patricia Santos Rossi, Gabriela Rodrigues Thomaz, Gabriela Garbossa, Mikael Neumann, and Heloisa Godoi Bertagnon. "Therapeutic efficacy of marbofloxacin and ceftiofur in feedlot steers with bovine respiratory disease complex." Acta Veterinaria Brasilica 16, no. 4 (December 9, 2022): 371–77. http://dx.doi.org/10.21708/avb.2022.16.4.10983.

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Treatment of the bovine respiratory disease complex (BRDC) can elicit high bacterial resistance and stress to steers in a feedlot. Therefore, the present study aimed to evaluate three therapeutic protocols with long-acting antibiotics against BRDC naturally acquired in steers finished in feedlot. In a total of 80 animals finished in a feedlot, 18 steers showed clinical signs compatible with BRDC (mucopurulent nasal secretion, lung auscultation alteration, leukocytosis, and decrease of dry matter intake). These animals were randomly treated: marbofloxacin in a single dose (M1), marbofloxacin in two doses (M2), or ceftiofur in a single dose (C1) on Day 0. The clinical score of pneumonia, hemogram, daily food intake, and body weight were analyzed during 7 days. On slaughter day (Day 100), the body weight and frequency of lungs with pneumonia was evaluated. On Day 7, M2 showed absence of pneumonia, and M1 and C1 still showed a clinical score of mild pneumonia (P = 0.01). On day 2 and day 3 M2 showed a higher dry matter intake than others treatments (P = 0.05). C1 showed a lower body weight than others group on day 1 and 2 (P = 0.05). The C1 and M1 showed a higher pneumonia frequency than M2 (P = 0.02). The M2 slaughter weight was numerically higher than the other treatments. We conclude the marbofloxacin in two doses eliminated the pneumonia ́s clinical symptoms and allowed the animals to return the productivity earlier than other protocols.

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Lennick, Michael, Shelesa A. Brew, and Kenneth C. Ingham. "Changes in protein conformation and stability accompany complex formation between human C1 inhibitor and C1.lovin.s." Biochemistry 24, no. 10 (May 7, 1985): 2561–68. http://dx.doi.org/10.1021/bi00331a025.

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Huisman, L. G. M., J. M. T. van Griensven, and C. Kluft. "On the Role of C1-Inhibitor as Inhibitor of Tissue-type Plasminogen Activator in Human Plasma." Thrombosis and Haemostasis 73, no. 03 (1995): 466–71. http://dx.doi.org/10.1055/s-0038-1653798.

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SummaryAn enzyme immuno assay was developed to measure complexes of tissue-type plasminogen activator (t-PA) with C1-inhibitor in order to study the role of C1-inhibitor as an inhibitor of t-PA in plasma. In vitro experiments with melanoma and recombinant t-PA learned that purified C1-inhibitor reacts with both single chain t-PA and two chain t-PA. The rate constants ranged from 3.0 to 5.2 M-1s-1 In plasma, melanoma and recombinant two chain t-PA were hardly inhibited by C1-inhibitor, in contrast to melanoma and recombinant single chain t-PA which were inhibited to the same extent by endogenous C1-inhibitor as they were by purified C1-inhibitor. In vivo, t-PA/C1-inhibitor complex could be measured in plasma in a few cases in healthy volunteers (0.62 ± 0.43 ng/ml t-PA equivalents), after exercise (0.84 ± 0.25 ng/ml t-PA equivalents) and after a desmopressin infusion (0.26 ± 0.04 ng/ml t-PA equivalents). However, t-PA/C1-inhibitor complex was found in plasma in all cases after venous occlusion (1.7 ± 0.5 ng/ml t-PA equivalents), in peritoneal fluid from patients suffering from peritoneal inflammatory disease (2.2 ± 1.3 ng/ml t-PA equivalents) and in plasma from healthy volunteers during a t-PA infusion (27.7 ± 18.5 ng/ml t-PA equivalents at peak level). In the last case, about 8 % of the infused dose of recombinant t-PA (alteplase) was inhibited by C1-inhibitor at peak level. The half-life (t1/2α) of t-PA antigen in plasma was found not to be altered when t-PA was inhibited by C1-inhibitor (4.0 min and 4.2 min, respectively). Thus, in vivo, t-PA/C1-inhibitor complex is mostly present when t-PA escapes rapid liver clearance and accumulates in one place (e.g. during venous occlusion or in peritoneal fluid) or when it circulates in high concentrations (e.g. during t-PA infusion).

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Qaiser, Jamal, Lee Yong Seong, Jeon Hyeon Deok, and Kim Kil Young. "Effect of plant growth-promoting bacteria Bacillus amylliquefaciens Y1 on soil properties, pepper seedling growth, rhizosphere bacterial flora and soil enzymes." Plant Protection Science 54, No. 3 (May 15, 2018): 129–37. http://dx.doi.org/10.17221/154/2016-pps.

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The Bacillus amyloliquefaciens Y1 strain was evaluated for its effects on soil properties, pepper seedling growth, rhizosphere bacterial flora and soil enzyme activities. Y1 solubilised insoluble phosphate, produced chitinase, and released siderophores in plate detection assay. In order to evaluate the plant growth promotion potential in vivo, strain Y1 was grown in media containing chitin powder and complex fertiliser. The pot experiment was conducted by treating pepper seedlings with C1/1 (Y1 culture, 50 ml), C2/3 (Y1 culture, 33 ml), C1/2 (Y1 culture, 25 ml), F1/1 (complex fertiliser, 50 ml), F1/2 (complex fertiliser, 25 ml), and W (water) at 10, 20, 30, 40, and 50 days after transplantation (DAT). Plants receiving Y1 had 52% (C1/2) and 68% (C1/1) more root and shoot biomass than W, and 14% (C1/1) and 18% (C2/3) more compared to F1/1 at 80 DAT. Total numbers of flowers per plant at 80 DAT were found significantly higher with the application of Y1 having 34 (C1/1), 35 (C2/3), and 22 (C1/2) compared to 4 (W), 12 (F1/1) and 10 (F1/2). In addition, chlorophyll content in pepper leaves was found to improve with the application of Y1. Furthermore, Y1 has significantly improved nutritional assimilation of total NPK, population of total culturable bacteria and chitinase producing bacteria and activities of chitinase and dehydrogenase in soil. At 60 and 80 DAT, the number of B. amyloliquefaciens at C1/1, C2/3, and C1/2 ranged from 2.3 × 10<sup>4</sup> to 4.6 × 10<sup>4</sup> CFU/g of soil. Our results concluded that B. amyloliquefaciens Y1 has positive effects on soil properties and can be suggested as a bio-fertiliser to minimise fertiliser application in modern agriculture.

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Menendez, Jose A., and Neill M. Wright. "TECHNIQUES OF POSTERIOR C1–C2 STABILIZATION." Neurosurgery 60, suppl_1 (January 1, 2007): S1–103—S1–111. http://dx.doi.org/10.1227/01.neu.0000249220.50085.e4.

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Abstract INSTABILITY OF THE atlantoaxial complex may result from inflammatory, traumatic, congenital, neoplastic, or degenerative disorders and often requires surgical stabilization. Initial dorsal wiring techniques allow safe fixation but require rigid external immobilization and have been associated with high fusion failure rates. Rigid screw fixation techniques including transarticular screw fixation and C1–C2 rod-cantilever fixation offer higher fusion rates and less need for rigid immobilization but are more technically demanding. C1–C2 fixation using crossing C2 laminar screws offers rigid fixation but without the technical demands of C2 pars placement. The history and techniques of dorsal fixation of the atlantoaxial complex are reviewed, and the success rates and complications of each are discussed.

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Steinmetz, Michael P., Thomas E. Mroz, and Edward C. Benzel. "Craniovertebral Junction." Neurosurgery 66, suppl_3 (March 1, 2010): A7—A12. http://dx.doi.org/10.1227/01.neu.0000366109.85796.42.

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Abstract THE CRANIOVERTEBRAL JUNCTION is a complex region that incorporates the occiput–C1–C2 portions of the spine. It is a transition between the cranium and the mobile cervical spine that permits significant motion. The motions afforded and the anatomy are vastly different at the occiput–C1 and C1–C2 articulations. These differences make treating pathology in this region very difficult. Problems include bony fixation of the cranium and the cervical spine (specifically C1 and C2), which limits complex motions, and limited bony sites available for arthrodesis. A thorough knowledge of the normal anatomy and biomechanics is required for fixation of this region. Moreover, an understanding of pathologic motions and the biomechanics of fixation is needed for successful construct design and good patient outcome.

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Hamel, Patrice, Claire Lemaire, Nathalie Bonnefoy, Paule Brivet-Chevillotte, and Geneviève Dujardin. "Mutations in the Membrane Anchor of Yeast Cytochrome c1 Compensate for the Absence of Oxa1p and Generate Carbonate-Extractable Forms of Cytochrome c1." Genetics 150, no. 2 (October 1, 1998): 601–11. http://dx.doi.org/10.1093/genetics/150.2.601.

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Abstract Oxa1p is a mitochondrial inner membrane protein that is mainly required for the insertion/assembly of complex IV and ATP synthase and is functionally conserved in yeasts, humans, and plants. We have isolated several independent suppressors that compensate for the absence of Oxa1p. Molecular cloning and sequencing reveal that the suppressor mutations (CYT1-1 to -6) correspond to amino acid substitutions that are all located in the membrane anchor of cytochrome c1 and decrease the hydrophobicity of this anchor. Cytochrome c1 is a catalytic subunit of complex III, but the CYT1-1 mutation does not seem to affect the electron transfer activity. The double-mutant cyt1-1,164, which has a drastically reduced electron transfer activity, still retains the suppressor activity. Altogether, these results suggest that the suppressor function of cytochrome c1 is independent of its electron transfer activity. In addition to the membranebound cytochrome c1, carbonate-extractable forms accumulate in all the suppressor strains. We propose that these carbonate-extractable forms of cytochrome c1 are responsible for the suppressor function by preventing the degradation of the respiratory complex subunits that occur in the absence of Oxa1p.

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Brier, Livia W., Liang Ge, Goran Stjepanovic, Ashley M. Thelen, James H. Hurley, and Randy Schekman. "Regulation of LC3 lipidation by the autophagy-specific class III phosphatidylinositol-3 kinase complex." Molecular Biology of the Cell 30, no. 9 (April 15, 2019): 1098–107. http://dx.doi.org/10.1091/mbc.e18-11-0743.

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Autophagy is a conserved eukaryotic pathway critical for cellular adaptation to changes in nutrition levels and stress. The class III phosphatidylinositol (PI)3-kinase complexes I and II (PI3KC3-C1 and -C2) are essential for autophagosome initiation and maturation, respectively, from highly curved vesicles. We used a cell-free reaction that reproduces a key autophagy initiation step, LC3 lipidation, as a biochemical readout to probe the role of autophagy-related gene (ATG)14, a PI3KC3-C1-specific subunit implicated in targeting the complex to autophagy initiation sites. We reconstituted LC3 lipidation with recombinant PI3KC3-C1, -C2, or various mutant derivatives added to extracts derived from a CRISPR/Cas9-generated ATG14-knockout cell line. Both complexes C1 and C2 require the C-terminal helix of VPS34 for activity on highly curved membranes. However, only complex C1 supports LC3 lipidation through the curvature-targeting amphipathic lipid packing sensor (ALPS) motif of ATG14. Furthermore, the ALPS motif and VPS34 catalytic activity are required for downstream recruitment of WD-repeat domain phosphoinositide-interacting protein (WIPI)2, a protein that binds phosphatidylinositol 3-phosphate and its product phosphatidylinositol 3, 5-bisphosphate, and a WIPI-binding protein, ATG2A, but do not affect membrane association of ATG3 and ATG16L1, enzymes contributing directly to LC3 lipidation. These data reveal the nuanced role of the ATG14 ALPS in membrane curvature sensing, suggesting that the ALPS has additional roles in supporting LC3 lipidation.

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Mondal, Avisek, Rajagopal Chattopadhyaya, Ajit Bikram Datta, and Pradeep Parrack. "Crystallization and X-ray analysis of the transcription-activator protein C1 of bacteriophage P22 in complex with the PREpromoter element." Acta Crystallographica Section F Structural Biology Communications 71, no. 10 (September 23, 2015): 1286–91. http://dx.doi.org/10.1107/s2053230x15015708.

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The transcription-activator protein C1 of the temperate phage P22 ofSalmonella typhimuriumplays a key role in the lyticversuslysogenic switch of the phage. A homotetramer of 92-residue polypeptides, C1 binds to an approximate direct repeat similar to the transcription activator CII of coliphage λ. Despite this and several other similarities, including 57% sequence identity to coliphage CII, many biochemical observations on P22 C1 cannot be explained based on the structure of CII. To understand the molecular basis of these differences, C1 was overexpressed and purified and subjected to crystallization trials. Although no successful hits were obtained for the apoprotein, crystals could be obtained when the protein was subjected to crystallization trials in complex with a 23-mer promoter DNA fragment (PRE). These crystals diffracted very well at the home source, allowing the collection of a 2.2 Å resolution data set. The C1–DNA crystals belonged to space groupP21, with unit-cell parametersa= 87.27,b= 93.58,c= 111.16 Å, β = 94.51°. Solvent-content analysis suggests that the asymmetric unit contains three tetramer–DNA complexes. The three-dimensional structure is expected to shed light on the mechanism of activation by C1 and the molecular basis of its specificity.

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Resnick, Daniel K., and Edward C. Benzel. "C1–C2 Pedicle Screw Fixation with Rigid Cantilever Beam Construct: Case Report and Technical Note." Neurosurgery 50, no. 2 (February 1, 2002): 426–28. http://dx.doi.org/10.1097/00006123-200202000-00039.

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ABSTRACT OBJECTIVE AND IMPORTANCE Transarticular screw fixation of the C1–C2 complex provides immediate rigid fixation of the unstable spine. The technique is not feasible in a certain proportion of patients because of the position of the vertebral artery or the patient's body habitus. CLINICAL PRESENTATION The authors describe a rigid screw technique for the surgical treatment of a woman who was excluded as a candidate for C1–C2 transarticular screw fixation. TECHNIQUE C1–C2 pedicle screw fixation was achieved using a fixed moment arm cantilever beam system. This system provided immediate rigid fixation of the C1–C2 complex in a patient who was not a candidate for transarticular screw fixation. CONCLUSION This technique is technically more forgiving than posterior transarticular screw fixation and may be applied to a broader spectrum of patients.

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Sobko, E. A., I. V. Demko, I. A. Solovieva, A. Yu Kraposhina, N. V. Gordeeva, and D. A. Anikin. "Complex clinical case: hereditary angioedema." Russian Medical Inquiry 5, no. 1 (2021): 50–53. http://dx.doi.org/10.32364/2587-6821-2021-5-1-50-53.

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Nowadays, isolated angioedema is one of the most complex and urgent problems of modern allergology and immunology. Hereditary angioedema (HA) refers to orphan and life-threatening diseases associated with a deficiency or decrease in C1-inhibitor function and is characterized by recurrent edema in deep dermis of various localization. A doctor of any specialty can encounter this nosology, which obliges all medical officers to have a general overview concerning HA. Late diagnosis is fraught with unnecessary surgical interventions, psychological symptoms, opiate addiction, or life-threatening laryngeal angioedema. To date, the final diagnosis of HA, and, consequently, adequate drug therapy, is delayed by an average of 8.5 years from disease onset. Sudden edema in the vital organs is a source of constant anxiety, a cause of disability, and sometimes fatal outcomes. The article presents a clinical case and discusses therapy principles, existing possibilities of promising treatment and recommendations for further management. KEYWORDS: hereditary angioedema, recurrent edema, orphan diseases, bradykinin; C1-inhibitor; complement system. FOR CITATION: Sobko E.A., Demko I.V., Solovieva I.A. et al. Complex clinical case: hereditary angioedema. Russian Medical Inquiry. 2021;5(1):50–53. DOI: 10.32364/2587-6821-2021-5-1-50-53.

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de los Campos, Gustavo, and Daniel A. Sorensen. "A commentary on Pitfalls of predicting complex traits from SNPs." Nature Reviews Genetics 14, no. 12 (November 18, 2013): 894. http://dx.doi.org/10.1038/nrg3457-c1.

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Scarr, Rebecca B., Matthew R. Smith, Margaret Beddall, and Phillip A. Sharp. "A Novel 50-Kilodalton Fragment of Host Cell Factor 1 (C1) in G0 Cells." Molecular and Cellular Biology 20, no. 10 (May 15, 2000): 3568–75. http://dx.doi.org/10.1128/mcb.20.10.3568-3575.2000.

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ABSTRACT Host cell factor 1 (HCF-1; also called C1) is a 230-kDa protein which is cleaved posttranslationally into separate but associated N- and C-terminal polypeptides. These polypeptides are components of the C1 complex, along with Oct-1 and the viral protein VP16. The C1 complex is formed when herpes simplex virus (HSV) infects a cell and is responsible for transcription of the HSV immediate-early genes. A temperature-sensitive mutation in the N-terminal kelch domain of HCF-1 reversibly arrests cells in a G0-like state when grown at the nonpermissive temperature, and the same domain interacts with VP16 in the formation of the C1 complex. The form of HCF-1 in primary G0 cells was investigated by using peripheral blood mononucleocytes and serum-arrested human primary fibroblasts. A novel 50-kDa N-terminal fragment of HCF-1 encompassing the kelch domain was identified in the cytoplasm of these cells. This fragment arises by proteolysis of the full-length HCF-1 protein and is able to associate with VP16.

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Young, Lindsey N., Felix Goerdeler, and James H. Hurley. "Structural pathway for allosteric activation of the autophagic PI 3-kinase complex I." Proceedings of the National Academy of Sciences 116, no. 43 (October 7, 2019): 21508–13. http://dx.doi.org/10.1073/pnas.1911612116.

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Autophagy induction by starvation and stress involves the enzymatic activation of the class III phosphatidylinositol (PI) 3-kinase complex I (PI3KC3-C1). The inactive basal state of PI3KC3-C1 is maintained by inhibitory contacts between the VPS15 protein kinase and VPS34 lipid kinase domains that restrict the conformation of the VPS34 activation loop. Here, the proautophagic MIT domain-containing protein NRBF2 was used to map the structural changes leading to activation. Cryoelectron microscopy was used to visualize a 2-step PI3KC3-C1 activation pathway driven by NRFB2 MIT domain binding. Binding of a single NRBF2 MIT domain bends the helical solenoid of the VPS15 scaffold, displaces the protein kinase domain of VPS15, and releases the VPS34 kinase domain from the inhibited conformation. Binding of a second MIT stabilizes the VPS34 lipid kinase domain in an active conformation that has an unrestricted activation loop and is poised for access to membranes.

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Krumdieck, R., M. Höök, L. C. Rosenberg, and J. E. Volanakis. "The proteoglycan decorin binds C1q and inhibits the activity of the C1 complex." Journal of Immunology 149, no. 11 (December 1, 1992): 3695–701. http://dx.doi.org/10.4049/jimmunol.149.11.3695.

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Abstract Decorin, a small collagen-binding dermatan sulfate proteoglycan, is widely distributed as a component of extracellular matrices. Using a solid phase binding assay, we showed that decorin bound C1q at physiologic pH and ionic strength. The interaction did not require divalent cations and was time and temperature dependent reaching equilibrium in 4 h at 37 degrees C. Binding was specific and saturable with an apparent dissociation constant of 7.6 x 10(-9) M. Decorin was shown to bind pepsin-derived fragments containing the collagenous domain of C1q and collagenase-derived fragments containing the globular domain of C1q. Because these fragments share a short sequence of amino acids, this finding suggests that decorin binds to a region of C1q located near the junction of the two domains. Competition studies using purified preparations of the decorin core protein and the glycosaminoglycan chains showed that only the former inhibited binding of decorin to C1q indicating that the interaction is mediated by the decorin core protein. Decorin was shown to inhibit the hemolytic activity of purified C1 as well as C1 in normal human serum. Approximately 50% inhibition was observed at a decorin concentration of 2 micrograms/ml. Inhibition was not observed if C1 was bound to Ag-complexed antibody. Furthermore, neither the core protein nor the glycosaminoglycan chain of decorin inhibited C1, indicating that the intact proteoglycan is necessary for functional activity.

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Bianchino, A. C., P. H. Poon, and V. N. Schumaker. "A mechanism for the spontaneous activation of the first component of complement, C1, and its regulation by C1-inhibitor." Journal of Immunology 141, no. 11 (December 1, 1988): 3930–36. http://dx.doi.org/10.4049/jimmunol.141.11.3930.

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Abstract We have developed a method to initiate spontaneous activation of the first component of complement in serum, by the removal of C1-inhibitor through complexation with added C1s. Preliminary experiments to test this method using C1 reconstituted from its purified subcomponents led to an unexpected result: pre-incubation of the reassembled subcomponents with C1-inhibitor, followed by its removal with C1s, altered the subsequent pattern of spontaneous activation. Thus, pre-incubation with C1-inhibitor at 37 degrees C for 1 h resulted in sigmoidal activation of C1 with a prolonged lag phase. In contrast, pre-incubation with C1-inhibitor on ice for the same time resulted in subsequent rapid, pseudo first order activation of C1 with a half-life of about 5 min. We have examined the activation kinetics under a variety of conditions, and our data are consistent with a model proposed by Lepow and coworkers in 1965, involving both spontaneous activation and C1 catalyzed activation: (1) C1----k1 C1 (2) C1----k2C1 C1 According to this model, the role of C1-inhibitor is to eliminate the second step by rapidly forming a tight complex with C1 which becomes irreversible at 37 degrees C. When C1s was added to normal human serum, activation at 37 degrees C was also sigmoidal, similar to that of reconstituted C1.

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Arlaud, G. J., C. Gaboriaud, N. M. Thielens, and V. Rossi. "Structural biology of Cl." Biochemical Society Transactions 30, no. 6 (November 1, 2002): 1001–6. http://dx.doi.org/10.1042/bst0301001.

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The classical complement pathway is a major element of innate immunity against infection, and is also involved in immune tolerance, graft rejection and various pathologies. This pathway is triggered by C1, a multimolecular protease formed from the association of a recognition protein, C1q, and a catalytic subunit, the calcium-dependent tetramer C1s-C1r-C1r-C1s, which comprises two copies of each of the modular proteases C1r and C1s. All activators of the pathway are recognized by the C1q moiety of C1, a process that generates a conformational signal that triggers self-activation of C1r, which in turn activates C1s, the enzyme that mediates specific cleavage of C4 and C2, the C1 substrates. Early work based on biochemical and electron microscopy studies has allowed characterization of the domain structure of the C1 subcomponents and led to a low-resolution model of the complex in which the elongated C1s-C1r-C1r-C1s tetramer folds into a compact, figure-of-8-shaped conformation upon interaction with C1q. The strategy used over the past decade was based on a dissection of the C1 proteins into modular segments to characterize their function and solve their three-dimensional structure by X-ray crystallography or NMR spectroscopy. This approach allows deep insights into the structure-function relationships of C1, particularly with respect to the assembly of the C1 complex and the mechanisms underlying its activation and proteolytic activity.

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Journal articles on the topic 'C1 Complex'

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