Academic literature on the topic 'Calcium cofactor'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Calcium cofactor.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Journal articles on the topic "Calcium cofactor"
1
Chaturvedi, Madhu, and Arun K. Shukla. "Calcium as a biased cofactor." Science 368, no. 6489 (April 23, 2020): 369–70. http://dx.doi.org/10.1126/science.abb4393.
Full text
2
Khatun, Mita, Md Mamun Monir, Ting Xu, Haiming Xu, and Jun Zhu. "Genome-wide conditional association study reveals the influences of lifestyle cofactors on genetic regulation of body surface area in MESA population." PLOS ONE 16, no. 6 (June 18, 2021): e0253167. http://dx.doi.org/10.1371/journal.pone.0253167.
Full textAbstract:
Body surface area (BSA) is an important trait used for many clinical purposes. People’s BSA may vary due to genetic background, race, and different lifestyle factors (such as walking, exercise, reading, smoking, transportation, etc.). GWAS of BSA was conducted on 5,324 subjects of four ethnic populations of European-American, African-American, Hispanic-American, and Chinese-American from the Multi-Ethnic Study of Atherocloris (MESA) data using unconditional and conditional full genetic models. In this study, fifteen SNPs were identified (Experiment-wise PEW < 1×10−5) using unconditional full genetic model, of which thirteen SNPs had individual genetic effects and seven SNPs were involved in four pairs of epistasis interactions. Seven single SNPs and eight pairs of epistasis SNPs were additionally identified using exercise, smoking, and transportation cofactor-conditional models. By comparing association analysis results from unconditional and cofactor conditional models, we observed three different scenarios: (i) genetic effects of several SNPs did not affected by cofactors, e.g., additive effect of gene CREB5 (a≙ –0.013 for T/T and 0.013 for G/G, −Log10 PEW = 8.240) did not change in the cofactor models; (ii) genetic effects of several SNPs affected by cofactors, e.g., the genetic additive effect (a≙ 0.012 for A/A and –0.012 for G/G, −Log10 PEW = 7.185) of SNP of the gene GRIN2A was not significant in transportation cofactor model; and (iii) genetic effects of several SNPs suppressed by cofactors, e.g., additive (a≙ –0.018 for G/G and 0.018 for C/C, −Log10 PEW = 19.737) and dominance (d≙ –0.038 for G/C, −Log10 PEW = 27.734) effects of SNP of gene ERBB4 was identified using only transportation cofactor model. Gene ontology analysis showed that several genes are related to the metabolic pathway of calcium compounds, coronary artery disease, type-2 Diabetes, Alzheimer disease, childhood obesity, sleeping duration, Parkinson disease, and cancer. This study revealed that lifestyle cofactors could contribute, suppress, increase or decrease the genetic effects of BSA associated genes.
3
Yong, S. C., P. Roversi, J. Lillington, F. Rodriguez, M. Krehenbrink, O. B. Zeldin, E. F. Garman, S. M. Lea, and B. C. Berks. "A complex iron-calcium cofactor catalyzing phosphotransfer chemistry." Science 345, no. 6201 (September 4, 2014): 1170–73. http://dx.doi.org/10.1126/science.1254237.
Full text
4
Hayakawa, Yumiko, Toshimitsu Hayashi, Jung-Bum Lee, Tetsuo Ozawa, and Nobuo Sakuragawa. "Activation of Heparin Cofactor II by Calcium Spirulan." Journal of Biological Chemistry 275, no. 15 (April 6, 2000): 11379–82. http://dx.doi.org/10.1074/jbc.275.15.11379.
Full text
5
Grinnell, BW, JD Walls, C. Marks, AL Glasebrook, DT Berg, SB Yan, and NU Bang. "Gamma-carboxylated isoforms of recombinant human protein S with different biologic properties." Blood 76, no. 12 (December 15, 1990): 2546–54. http://dx.doi.org/10.1182/blood.v76.12.2546.2546.
Full textAbstract:
Abstract Human protein S (HPS), a regulator of hemostasis, is a vitamin K- dependent plasma protein with potential clinical utility. We have obtained high-level expression of the cDNA for HPS in two mammalian cell lines. Both cell lines secreted single chain recombinant HPS (rHPS) in serum-free medium as determined by Western blot analysis. The ability of the rHPS from both cell lines to act as a cofactor for human protein C (HPC) was determined; the rHPS secreted from the human 293 cell line had an activity six times that of the rHPS from the AV12–664 Syrian hamster cell line. Furthermore, the relative specific cofactor activity of rHPS from the 293 cell line was actually 2.5-fold higher than that of single-chain human plasma-derived HPS. Essentially all of the rHPS secreted from the 293 cell line exhibited a calcium-dependent elution profile on anion exchange chromatography, whereas only 25% to 35% of the hamster cell-derived rHPS exhibited this profile. However, the calcium-eluted rHPS from the AV12 cell line had a high specific cofactor activity, equivalent to that of the 293-derived rHPS. A NaCl- elutable rHPS fraction (calcium nondependent) was isolated from the recombinant AV12–664 cell line, further purified, and found to have reduced activity, only 40% that of the calcium-dependent rHPS. The only observable difference in the calcium-dependent and nondependent rHPS molecules was in the content of gamma-carboxyglutamic acid (Gla); the calcium-dependent material contained approximately 10 mol Gla/mol protein whereas the calcium-nondependent material contained only approximately 8 mol Gla/mol of protein. In addition, the calcium- nondependent rHPS had reduced ability to interact with phospholipid vesicles as evidenced by an eightfold increase in the apparent kd. Our data demonstrate the isolation of rHPS with high specific activity, and show that a reduction in as few as two Gla residues dramatically decreases its functional cofactor activity for HPC, due to a reduction in ability to interact with the phospholipid bilayer.
6
Grinnell, BW, JD Walls, C. Marks, AL Glasebrook, DT Berg, SB Yan, and NU Bang. "Gamma-carboxylated isoforms of recombinant human protein S with different biologic properties." Blood 76, no. 12 (December 15, 1990): 2546–54. http://dx.doi.org/10.1182/blood.v76.12.2546.bloodjournal76122546.
Full textAbstract:
Human protein S (HPS), a regulator of hemostasis, is a vitamin K- dependent plasma protein with potential clinical utility. We have obtained high-level expression of the cDNA for HPS in two mammalian cell lines. Both cell lines secreted single chain recombinant HPS (rHPS) in serum-free medium as determined by Western blot analysis. The ability of the rHPS from both cell lines to act as a cofactor for human protein C (HPC) was determined; the rHPS secreted from the human 293 cell line had an activity six times that of the rHPS from the AV12–664 Syrian hamster cell line. Furthermore, the relative specific cofactor activity of rHPS from the 293 cell line was actually 2.5-fold higher than that of single-chain human plasma-derived HPS. Essentially all of the rHPS secreted from the 293 cell line exhibited a calcium-dependent elution profile on anion exchange chromatography, whereas only 25% to 35% of the hamster cell-derived rHPS exhibited this profile. However, the calcium-eluted rHPS from the AV12 cell line had a high specific cofactor activity, equivalent to that of the 293-derived rHPS. A NaCl- elutable rHPS fraction (calcium nondependent) was isolated from the recombinant AV12–664 cell line, further purified, and found to have reduced activity, only 40% that of the calcium-dependent rHPS. The only observable difference in the calcium-dependent and nondependent rHPS molecules was in the content of gamma-carboxyglutamic acid (Gla); the calcium-dependent material contained approximately 10 mol Gla/mol protein whereas the calcium-nondependent material contained only approximately 8 mol Gla/mol of protein. In addition, the calcium- nondependent rHPS had reduced ability to interact with phospholipid vesicles as evidenced by an eightfold increase in the apparent kd. Our data demonstrate the isolation of rHPS with high specific activity, and show that a reduction in as few as two Gla residues dramatically decreases its functional cofactor activity for HPC, due to a reduction in ability to interact with the phospholipid bilayer.
7
Armstrong, C. M., and G. Cota. "Calcium ion as a cofactor in Na channel gating." Proceedings of the National Academy of Sciences 88, no. 15 (August 1, 1991): 6528–31. http://dx.doi.org/10.1073/pnas.88.15.6528.
Full text
8
Hayakawa, Y., T. Hayashi, K. Hayashi, T. Hayashi, T. Ozawa, K. Niiya, and N. Sakuragawa. "Heparin cofactor II-dependent antithrombin activity of calcium spirulan." Blood Coagulation & Fibrinolysis 7, no. 5 (July 1996): 554–60. http://dx.doi.org/10.1097/00001721-199607000-00007.
Full text
9
Saif, Muhammad Wasif, Nektaria Makrilia, and Kostas Syrigos. "CoFactor: Folate Requirement for Optimization of 5-Fluouracil Activity in Anticancer Chemotherapy." Journal of Oncology 2010 (2010): 1–5. http://dx.doi.org/10.1155/2010/934359.
Full textAbstract:
Intracellular reduced folate exists as a “pool” of more than 6 interconvertable forms. One of these forms, 5,10 methylenetetrahydrofolic acid (CH2THF), is the key one-carbon donor and reduced folate substrate for thymidylate synthase (TS). This pathway has been an important target for chemotherapy as it provides one of the necessary nucleotide substrates for DNA synthesis. The fluoropyrimidine 5-fluorouracil (5-FU) exerts its main cytotoxic activity through TS inhibition. Leucovorin (5-formyltetrahydrofolate; LV) has been used to increase the intracellular reduced folate pools and enhance TS inhibition. However, it must be metabolized within the cell through multiple intracellular enzymatic steps to form CH2THF. CoFactor (USAN fotrexorin calcium, (dl)-5,10,-methylenepteroyl-monoglutamate calcium salt) is a reduced folate that potentiates 5-FU cytotoxicity. According to early clinical trials, when 5-FU is modulated by CoFactor instead of LV, there is greater anti-tumor activity and less toxicity. This review presents the emerging role of CoFactor in colorectal and nongastrointestinal malignancies.
10
Hayakawa, Yumiko, Yutaka Hirashima, Hiromichi Yamamoto, Masanori Kurimoto, Toshimitsu Hayashi, Jung-Bum Lee, and Shunro Endo. "Mechanism of activation of heparin cofactor II by calcium spirulan." Archives of Biochemistry and Biophysics 416, no. 1 (August 2003): 47–52. http://dx.doi.org/10.1016/s0003-9861(03)00289-3.
Full textDissertations / Theses on the topic "Calcium cofactor"
1
Hendry, Garth S., and Garth Hendry@baldwins com. "Dependence of substrate-water binding on protein and inorganic cofactors of photosystem II." The Australian National University. Research School of Biological Sciences, 2002. http://thesis.anu.edu.au./public/adt-ANU20041124.140348.
Full textAbstract:
The photosynthetic water oxidation reaction is catalyzed by an inorganic Mn4OxCaClyHCO3-z cluster at the heart of the oxygen evolving complex (OEC) in photosystem II. In the absence of an atomic resolution crystal structure, the precise molecular organization of the OEC remains unresolved. Accordingly, the role of the protein and inorganic cofactors of PSII (Ca2+, HCO3- and Cl-) in the mechanism of O2-evolution await clarification. In this study, rapid 18O-isotope exchange measurements were applied to monitor the substrate-water binding kinetics as a function of the intermediate S-states of the catalytic site (i.e. S3, S2 and S1) in Triton X-100 solubilized membrane preparations that are enriched in photosystem II activity and are routinely used to evaluate cofactor requirements. Consistent with the previous determinations of the 18O exchange behavior in thylakoids, the initial 18O exchange measurements of native PSII membranes at m/e = 34 (which is sensitive to the 16O18O product) show that the fast and slowly exchanging substrate-waters are bound to the catalytic site in the S3 state, immediately prior to O2 release. Although the slowly exchanging water is bound throughout the entire S-state cycle, the kinetics of the fast exchanging water remains too fast in the S2, S1 [and S0] states to be resolved using the current instrumentation, and left open the possibility that the second substrate-water only binds to the active site after the formation of the S3 state. Presented is the first direct evidence to show that fast exchanging water is already bound to the OEC in the S2 state. Rapid 18O-isotope exchange measurements for Ex-depleted PSII (depleted of the 17- and 23-kDa extrinsic proteins) in the S2 state reveals a resolvable fast kinetic component of 34k2 = 120 ± 14 s-1. The slowing down of the fast phase kinetics is discussed in terms of increased water permeation and the effect on the local dielectric following removal of the extrinsic subunits. In addition, the first direct evidence to show the involvement of calcium in substrate-water binding is also presented. Strontium replacement of the OEC Ca2+-site reveals a factor of ~3-4 increase in the 18O exchange of the slowly exchanging water across the S3, S2 and S1 states while the kinetics of the fast exchanging water remain unchanged. Finally, a re-investigation of the proposed role for bicarbonate as an oxidizable electron donor to photosystem II was unable to discern any 18O enrichment of the photosynthetically evolved O2 in the presence of 18O-bicarbonate. A working model for O2-evolution in terms of these results is presented.
2
Hendry, Garth S. "Dependence of substrate-water binding on protein and inorganic cofactors of photosystem II." Phd thesis, 2002. http://hdl.handle.net/1885/47151.
Full textAbstract:
The photosynthetic water oxidation reaction is catalyzed by an inorganic Mn4OxCaClyHCO3-z cluster at the heart of the oxygen evolving complex (OEC) in photosystem II. In the absence of an atomic resolution crystal structure, the precise molecular organization of the OEC remains unresolved. Accordingly, the role of the protein and inorganic cofactors of PSII (Ca2+, HCO3- and Cl-) in the mechanism of O2-evolution await clarification. In this study, rapid 18O-isotope exchange measurements were applied to monitor the substrate-water binding kinetics as a function of the intermediate S-states of the catalytic site (i.e. S3, S2 and S1) in Triton X-100 solubilized membrane preparations that are enriched in photosystem II activity and are routinely used to evaluate cofactor requirements. Consistent with the previous determinations of the 18O exchange behavior in thylakoids, the initial 18O exchange measurements of native PSII membranes at m/e = 34 (which is sensitive to the 16O18O product) show that the ‘fast’ and ‘slowly’ exchanging substrate-waters are bound to the catalytic site in the S3 state, immediately prior to O2 release. Although the slowly exchanging water is bound throughout the entire S-state cycle, the kinetics of the fast exchanging water remains too fast in the S2, S1 [and S0] states to be resolved using the current instrumentation, and left open the possibility that the second substrate-water only binds to the active site after the formation of the S3 state. Presented is the first direct evidence to show that fast exchanging water is already bound to the OEC in the S2 state. Rapid 18O-isotope exchange measurements for Ex-depleted PSII (depleted of the 17- and 23-kDa extrinsic proteins) in the S2 state reveals a resolvable fast kinetic component of 34k2 = 120 ± 14 s-1. The slowing down of the fast phase kinetics is discussed in terms of increased water permeation and the effect on the local dielectric following removal of the extrinsic subunits. In addition, the first direct evidence to show the involvement of calcium in substrate-water binding is also presented. Strontium replacement of the OEC Ca2+-site reveals a factor of ~3-4 increase in the 18O exchange of the slowly exchanging water across the S3, S2 and S1 states while the kinetics of the fast exchanging water remain unchanged. Finally, a re-investigation of the proposed role for bicarbonate as an oxidizable electron donor to photosystem II was unable to discern any 18O enrichment of the photosynthetically evolved O2 in the presence of 18O-bicarbonate. A working model for O2-evolution in terms of these results is presented.
Books on the topic "Calcium cofactor"
1
Chakera, Aron, William G. Herrington, and Christopher A. O’Callaghan. Disorders of plasma magnesium. Edited by Patrick Davey and David Sprigings. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780199568741.003.0177.
Full textAbstract:
Normal serum magnesium levels are in the range of 0.7–1.0 mmol/l and, as for calcium, most of the total body magnesium is found in bone and soft tissues. Magnesium is essential for normal cell metabolism (as a cofactor for numerous enzymes) and for neuronal function, and regulates parathyroid hormone release. Alterations in serum magnesium levels are usually asymptomatic unless severe. As there are large tissue reserves of magnesium, hypomagnesaemia usually only develops with chronic gastrointestinal or renal losses, or prolonged dietary insufficiency. Hypermagnesaemia is almost always iatrogenic, due to excessive supplementation. This chapter reviews the causes and management of derangements of plasma magnesium.
2
Calcium, The Facts: Get Maximum Benefits from Fossilized Coral and Important Cofactors (Health Learning Handbook) (Health Learning Handbook). Bl Publications, 2001.
Find full textBook chapters on the topic "Calcium cofactor"
1
Dudel, J. "Calcium, A Cofactor in Neuromuscular Transmission." In Calcium Electrogenesis and Neuronal Functioning, 155–65. Berlin, Heidelberg: Springer Berlin Heidelberg, 1986. http://dx.doi.org/10.1007/978-3-642-70744-5_14.
Full text
2
van Gorkom, Hans J., and Charles F. Yocum. "The Calcium and Chloride Cofactors." In Advances in Photosynthesis and Respiration, 307–27. Dordrecht: Springer Netherlands, 2005. http://dx.doi.org/10.1007/1-4020-4254-x_14.
Full text
3
Fernandez, Carmen, Roehl M. Cinco, John H. Robblee, Johannes Messinger, Shelly A. Pizarro, Kenneth Sauer, Melvin P. Klein, and Vittal K. Yachandra. "Calcium and Chloride Cofactors of the Oxygen Evolving Complex - X-Ray Absorption Spectroscopy Evidence for A Mn/Ca/Cl Heteronuclear Cluster." In Photosynthesis: Mechanisms and Effects, 1399–402. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-3953-3_330.
Full text
4
S.N. Chaitanya, Nyshadham, and Sibani Sahu. "Mineral Deficiencies a Root Cause for Reduced Longevity in Mammals." In Mineral Deficiencies - Genes, Diet and Disease Interface [Working Title]. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.94276.
Full textAbstract:
Metals, inorganic compounds and their elements that act as cofactors for enzymes that play an essential role in various biological processes constitute mineral nutrients. Their primary source is soil and enters the climax consumers in food chain through plants as they contain most minerals that are essential for humans. They are required in small and precise amounts according to their requirement they were classified as Major (phosphorous (P), potassium (K)), Secondary (calcium (Ca), magnesium (Mg), sulphur (S)), Minor/trace/rare (Boron (B), chlorine (Cl), chromium (Cr), fluoride(F), iodine (I), iron (Fe), manganese (Mn), molybdenum (Mo), nickel (Ni), selenium (Se), sodium (Na), vanadium (V) and zinc (Zn)). The daily requirement of minerals for individuals for effective biological function inside the cell is known as recommended dietary allowance (RDA) that varies for element. The daily requirement of major element is up to 10 g/d, whereas secondary and micro minerals was 400 - 1500 mg/d and 45 μg/d - 11 mg/d, respectively. Meats, vegetables, fruits, grains contains high amount of minerals that protect humans from mineral deficiencies. Some of the mineral deficiencies include ageing, cancer, hair loss etc. The key for these root problems include supplementation of healthy foods rich in minerals and understanding the importance of food by nutrition education, practice of physical activity, and about food habits. A detailed understanding of each mineral and their biological importance through mechanism of action studied in detail to overcome their deficiencies.
Conference papers on the topic "Calcium cofactor"
1
Dahiback, Bjorn, Ake Lundwall, Andreas Hillarp, Johan Malm, and Johan Stenflo. "STRUCTURE AND FUNCTION OF VITAMIN K-DEPENDENT PROTEIN S, a cofactor to activated protein C which also interacts with the complement protein C4b-binding protein." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1642960.
Full textAbstract:
Protein S is a single chain (Mr 75.000) plasma protein. It is a cofactor to activated protein C (APC) in the regulation of coagulation factors Va and Villa. It has high affinity for negatively charged phospolipids and it forms a 1:1 complex with APC on phospholipid surfaces, platelets and on endothelial cells. Patients with heterozygous protein S deficiency have a high incidence of thrombosis. Protein S is cleaved by thrombin, which leads to a loss of calcium binding sites and of APC cofactor activity. Protein S has two to three high affinity (KD 20uM) calcium binding sites - unrelated to the Gla-region - that are unaffected by the thrombin cleavage. In human plasma protein S (25 mg/liter) circulates in two forms; free (approx. 40%) and in a 1:1 noncovalent complex (KD 1× 10-7M) with the complement protein C4b-binding protein (C4BP). C4BP (Mr 570.000) is composed of seven identical 70 kDa subunits that are linked by disulfide bonds. When visualized by electron microscopy, C4BP has a spiderlike structure with the single protein S binding site located close to the central core and one C4b-binding site on each of the seven tentacles. When bound to C4BP, protein S looses its APC cofactor activity, whereas the function-of C4BP is not directly affected by the protein S binding. Chymotrypsin cleaves each of the seven C4BP subunits close to the central core which results in the liberation of multiple 48 kDa “tentacte” fragments and the formation of a 160 kDa central core fragment. We have successfully isolated a 160 kDa central core fragment with essentially intact protein S binding ability.The primary structure of both bovine and human protein S has been determined and found to contain 635 and 634 amino acids, respectively, with 82 % homology to each other. Four different regions were distinguished; the N-terminal Gla-domain (position 1-45) was followed by a region which has two thrombin-sensitive bonds positioned within a disulfide loop. Position 76 to 244 was occupied by four repeats homologous to the epidermal growth factor (EGF) precursor. In the first EGF-domain a modified aspartic acid was identified at position 95, B-hydroxaspartic acid (Hya), and in corresponding positions in the three following EGF-domains (positions 136,178 and 217) we found B-hydroxyasparagine (Hyn). Hyn has not previously been identified in proteins. The C-terminal half of protein S (from position 245) shows no homology to the serine proteases but instead to human Sexual Hormon Binding Globulin (SHBG)(see separate abstract). To study the structure-function relationship we made eighteen monoclonal antibodies to human protein S. The effects of the monoclonals on the C4BP-protein S interaction and on the APC cofactor activity were analysed. Eight of the antibodies were calciumdependent, four of these were against the Gla-domain, two against the thrombin sensitive portion and two against the region bearing the high affinity calcium binding sites. Three of the monoclonals were dependent on the presence of chelating agents, EDTA or EGTA, and were probably directed against the high affinity calcium binding region. Three other monoclonals inhibited the protein S-C4BP interaction. At present, efforts are made to localize the epitopes to gain information about functionally important regions of protein S.
2
Tran, T. H., U. Zuhlke, J. Hauert, F. Duckert, G. A. Marbet, and R. Wagenwoord. "INFLUENCE OF HEPARIN ON FACTOR VIII (FVIII) ASSAY." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644031.
Full textAbstract:
Thrombin-activated FVIII accelerates the conversion of factor X to activated factor X (FXa) by activated factor IX, phospholipids and calcium ions. In plasma, FVIII is activated by initial traces of thrombin, which, in the presence of heparin, is rapidly inhibited by binding to anti thrombin III and heparin cofactor II. To avoid the effect, we have experienced with increasing amounts of exogenous thrombin. We were able to match the heparin cofactors concentration in diluted plasma with thrombin, so that the presence of heparin did not affect the formation of FXa, whose activity was assessed with a chromogenic substrate. Indeed, addition of heparin at any concentration to citrated plasma showed no significant deviation from the FVIII control value. Levels of FVIII in heparinized plasmas similar to those in citrated plasmas further confirmed the finding. Patients plasmas showed comparable FVIII levels before and after heparin infusion, though plasma PTT was clearly prolonged after in vivo heparinization. FVIII chromogenic assay was correlated with the one-stage clotting assay by measuring FVIII levels in 60 hemophiliacs A and carriers, in patients with von Willebrand disease (27) and other congenital deficiencies (4), high risk of thrombosis (15), bleeding tendency (20), disseminated intravascular coagulation (4) and circulating anticoagulants (2), and commercial concentrates. There was a highly significant correlation between both techniques (N=127, r=0.97, Y=0.91X + 4, range 1-380%). Three severe hemophiliacs with were detected with both methods. Data obtained from both techniques were also in good agreement in the range of 1-20% FVIII.Thrombin was added both to activate instantaneously FVIII and to neutralize heparin cofactors in samples. It thus abolishes the incubation time needed to generate in situ traces of thrombin and the influence of heparin on our FVIII assay. An eventual fibrin formation does not affect the FXa formation and the reading. The technique is also suited for automation.
3
Omar, M. N., C. D. Lee, and K. G. Mann. "INACTIVATION OF FACTOR Va BY PIASMIN." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643883.
Full textAbstract:
The inactivation of Factor Va by plasmin was studied in the presence and absence of phospholipid vesicles and calcium ions. The action of plasmin resulted in a rapid loss of the ability of Factor Va to serve as a cofactor to Factor Xa , as judged by clotting assays and . direct assays of prothrombin activation using the fluorophore, dansylarginine N-(3-ethyl-1,5-pentanediyl) amide (DAPA) . The rate of Factor Va inactivation catalyzed by plasmin was markedly enhanced by the addition of phospholipid vesicles (PCPS), suggesting that the action of plasmin on Factor Va may be a membrane bound phenomena. Both Factor Xa and prothrombin were capable of protecting Factor Va from inactivation by plasmin. SDS-PAGE was utilized to correlate plasmin catalyzed proteolysis of Factor Va with the concomitant loss of activity. Data obtained with Factor Va and the isolated chains of the cofactor indicated that the light chain (E) was cleaved by plasmin to yield products similar to those obtained with Factor Xa and Activated Protein C (APC). The heavy chain (D) was found to be degraded by plasmin to produce proteolytic fragments distinct from those produced by Factor Xa and APC. The action of plasmin on single chain Factor V was notable for an initial, transient increase in total Factor V activity, followed by subsequent loss of activity, indicating the transient formation of active intermediates. SDS-PAGE analysis revealed the degradation of Factor V by plasmin to final, inactive products via several transient, higher molecular weight intermediates. These findings may be of some significance in pathophysiologic states in which systemic fibrinolysis may occur, possibly contributing to the depletion of clotting factors. The identification of such ongoing processes may eventually be facilitated by the observation that the degradation of Factor Va by plasmin leads to end products which may be unique to this interaction.(Supported by NIH Grants HL-35058 and HL 34575)
4
Krishnaswamy, S., K. Jones, and K. Mann. "STOPPED-FLOW KINETICS OF PROTHROMBINASE COMPLEX ASSEMBLY." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643279.
Full textAbstract:
Prothrombinase is the multi -component enzyme composed of factor Xa and the cofactor, factor Va, that assemble on a phospholipid surface in the presence of calcium ion. Fluoresence stopped-flow kinetic studies of prothrombinase assembly in the absence of the substrate, prothrombin were undertaken at saturating concentrations of calcium ion, using phospholipid vesicles (PCPS), factor Va and factor Xa modified at the active-site with the fluorophore dansyl-glutamylglycinylarginylchloro methylketone (DEGR-Xa). The substantial fluorescence enhancement of DEGR-Xa in the presence of factor Va, PCPS and calcium ion was used as a continuous measure of prothrombinase complex formation. The rate of complex formation studied under pseudo-first order conditions was most rapid when factor Va was reacted with the DEGR-Xa-PCPS binary complex. Under these conditions, the rate increased linearly with increasing PCPS concentrations and was independent of the concentration of factor Va. The reaction between Va and PCPS assessed by stopped-flow light scattering produced identical rates. The data indicate that the rate-limiting step in the reaction between Va and PCPS-bound DEGR-Xa is the initial formation of a Va-PCPS binary complex (8.4×107M−1s−1) followed by the very rapid reaction (>3×109M−1s−1) between PCPS-bound DEGR-Xa and Va. When complex formation was initiated by mixing DEGR-Xa and Va with PCPS or by mixing DEGR-Xa with Va-PCPS, the pseudo-first order rates were substantially lower. Under these conditions, increasing concentrations of factor Va inhibited the rate of prothrombinase complex formation which could be overcome by increasing PCPS concentrations. The data are consistent with the interpretation that the initial formation of the DEGR-Xa-PCPS complex is a prerequisite for prothrombinase assembly. The second order rate constant for the reaction between DEGR-Xa and PCPS (9.5×109M−1s−1 ) was independently determined by stopped-flow light scattering. Collectively, the data indicate that prothrombinase assembly proceeds via the initial formation of DEGR-Xa-PCPS and Va-PCPS binary complexes. The lipid-bound constituents then rapidly react via diffusion over the vesicle surface to form prothrombinase.(Supported by NIH grants HL-35058 and HL-34575)
5
Joost, S., A. Koedam, Joost C. M. Meijers, Jan J. Sixma, and Bonno N. Bouma. "VON WILLEBRAND FACTOR PROTECTS FACTOR VIII FROM INACTIVATION BY ACTIVATED PROTEIN C AND PROTEIN S." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643618.
Full textAbstract:
Activated protein C (APC) inactivated the cofactors factor V (FV) and factor VIII (FVIII). In the case of FV, this reaction and the respective roles of Ca2+ , phospholipids and protein S have been well documented. We investigated the role of protein S and von Willebrand factor (VWF) on the inactivation of FVIII.Purified human factor VIII (3 units/ml) was incubated with protein C (0.2 μg/ml) in the presence of 8 μg/ml phospholipid, 5 mM CaCl, and 1 unit/ml hirudin. Factor VIII coagulant activity decreased with a pseudo first-order rate constant of 0.09 min . The reaction rate increased linearly with the concentration of prot^ig S in the incubation mixture. 12I-FVIII was incubated under the same conditions. SDS-polyacrylamide gel electrophoresis showed cleavage products of Mr 43 and 22 kDa. High Mr bands (FVIII-heavy chain) ranging fromMr 108 to208 kDa disappeared while the Mr 80 kDa FVIII-lightchain remained unchanged. The degradationpattern was not changed by addition of protein S.The FVIII-VWF complex was reconstitutedby mixing the two components (±2 units VWF/units FVIII) and lowering the calcium concentration to 2 mM. The inactivation of the FVIII-VWF complex by APC proceeded at a 15- to 20-fold slower rate as compared to the isolated FVIII, indicating a protection of FVIII by VWF. Protein S exhibited no cofactor activity on the inactivation of FVIII-VWF by APC. The protective effect of VWF was lost completely after activation of the FVIII-VWF complexwith thrombin (0.05 units/ml).When FVIII (0.1 units/ml) was added toplasma of a patient with severe von Willebrand's disease, 96% of its activitywas lost in 20 min after the addition of APC. All of the FVIII activity was retained when haemophilic plasma was used. Mixing experiments showed that one unit ofVWF unit FVIII is needed to fully protec FVIII against APC. These results may explain the observed lability of FVIII in von Willebrand's disease patients.
6
Chediak, J., J. Eldridge, D. Sobel, B. Maxey, J. Baron, and M. C. Telfer. "FURTHER EVIDENCES OF VON WILLEBRAND FACTOR INVOLVEMENT IN THROMBOTIC THROMBOCYTOPENIC PURPURA (TTP)." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644587.
Full textAbstract:
Laboratory findings of TTP include severe thrombocytopenia and marked anemia due to intravascular hemolysis. The pathogenesis of the thrombocytopenia is poorly understood. Possible mechanisms include the presence of a platelet aggregating factor (JCI 76:1330, 1935), a calcium dependent protease (Blood 63:310a, 1986), abnormal prostaglandin production or metabolism, and an excessive consumption of high molecular weight forms of von Uillebrand factor (VUF). Von Willebrand factor proteins from 12 patients (pts) diagnosed as having TTP were studied. They include 8 females and 4 males; nine were studied during the acute presentation and seven pts also during the remission period. Three pts died during the acute event. None of the pts had a recurrence. Control subjects include both normal individuals and thrombocytopenic pts due to a variety of underlying diseases including marrow aplasia and immune thrombocytopenia, but excluding pts with DIC or suffering infection. Plasmas were tested for VWF antigen and Ristocetin Cofactor (RiCof) activity. The electrophoretic mobility (CIE) of VWF:Ag was also assessed and the ratio VWF:RiCof to VWF:Ag was determined. Statistical analysis including p values will be reported. Results:These results suggest that during the acute event there is an excessive consumption of large VWF multimers and the ratio VWF:RiCof/VWF:Ag could be used to corroborate the diagnosis of TTP and by doing sequential measurements to monitor the response to therapy.
7
Fay, P. J., S. I. Chavin, and F. J. Walker. "INACTIVATION OF FACTOR VIII BY ACTIVATED PROTEIN C AND PROTEIN S." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644770.
Full textAbstract:
Human factor VIII has been isolated from factor VIII concentrates. The isolated protein is composed of a heavy chain and light chain. The heavy chain was heterogenous with respect to molecular weight ranging from 110-170 kDa. The light chain appeared as a 81/84 kDa dimer, 'when factor VIII was treated with activated protein C in the presence of calcium and phospholipids factor VIII procoagulant activity was rapidly lost. Analysis of the activated protein C catalyzed cleavage products of factor VIII indicated that loss of activity was correlated with cleavage of the heavy chains. The heavy chains appeared to be converted into 93 kDa and 53 kDa peptides. A separate factor VIII preparation has been prepared that contained only a 93 kDa heavy chain as well as the 81/83 kDa light chain. When this preparation was inactivated with activated protein C, a pathway in which the 93 kDa peptide was degraded into a 68 kDa peptide which was subsequently degraded into 48 and 23 kDa polypeptides. This result suggested that the 53 kDa polypeptide was not derived from the 93 kDa domain of the heavy chain, but must have been derived from the variable molecular weight portion of the heavy chain. These results suggest that activated protein C catalyzed a minimum of four cleavages in the heavy chain. Activated protein C did not appear to alter the factor VIII light chain. Protein S has been observed to be a protein cofactor both the anticoagulant and proteolytic action of activated protein C with factor Va. It is thought that protein S forms a lipid bound complex with activated protein C which then can rapidly inactivate factor Va. When factor VIII was inactivated in the presence of both activated protein C and protein S the rate of activity loss was enhanced. The effect of protein S could be observed on the cleavage of the heavy chains and on secondary cleavages of the smaller products including the 93, 68, and 53 kDa polypeptides. In an analogous reaction, the addition of factor Xa has been observed to inhibit the inactivation of factor Va by activated protein C. The addition of factor IX to the factor Vlll-activated protein C reaction mixture resulted in the inhibition of factor VIII inactivation. The effect of factor IX was dose dependent. Finally, as both factor Va and factor VIII have structural similarities and are substrates for activated protein C the possibility that they might compete as substrates was tested. Factor VIII was observed to compete with factor Va for activated protein C. The concentration dependence of factor VIII inhibition of factor Va inactivation suggested that factor VIII and factor Va were equivalent substrates for activated protein C.
8
Waart, P. v. d., K. T. Preissner, U. Delvos, and G. Müller-Berghaus. "SIMULTANEOUS PRODUCTION OF ENDOTHELIAL CELL-DERIVED PROTEIN S AND FACTOR V, AND INACTIVATION OF FACTOR Va AT THE ENDOTHELIAL CELL SURFACE." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644737.
Full textAbstract:
Several proteins synthesized and expressed by endothelial cells are involved in the regulation of coagulation. The synthesis and expression of factor V and protein S has been demonstrated in independent studies. The present work evaluates the simultaneous synthesis and expression of bovine factor V and protein S and the effect of endothelial protein S on the inactivation of endothelial factor Va by activated protein C. The accumulation of both proteins in conditioned medium was detected by SDS-PAGE followed by immunoblotting, and their activities were tested by functional assays. The synthesis of protein S and factor V per 105 cells over 24 h amounted up to 2 ng protein S and 440 ng factor V, respectively. The addition of thrombin did not increase the yield of synthesized cofactors. Thrombin did neither proteolyse protein S on endothelial cells nor in a purified system in the presence of thrombomodulin and calcium ions. Factor V was secreted partly in its activated form as evidenced by the appearance of active intermediates with M = 220,000-280,000 on immunoblots as well as by only a three-Fold further activation of factor V/Va following addition of thrombin. The rate constant for the inactivation of factor Va by activated protein C was only two-fold higher for factor Va derived from cells cultured in the presence of vitamin K as compared in the presence of warfarin. For the inactivation of comparable factor Va concentrations in conditioned medium a 10-fold higher and on endothelial cells a 40-fold higher concentration of activated protein C was required to obtain similar inactivation rates of factor Va as compared to a purified system. These results suggest that resting endothelial cells contain a factor V activator, and that a regulatory mechanism is operative on the endothelial cell surface that suppresses the inactivation potential of activated protein C/ protein S.
Reports on the topic "Calcium cofactor"
1
Cinco, Roehl M. X-ray absorption spectroscopy on the calcium cofactor to the manganese cluster in photosynthetic oxygen evolution. Office of Scientific and Technical Information (OSTI), December 1999. http://dx.doi.org/10.2172/764364.
Full text
2
Nelson, Nathan, and Charles F. Yocum. Structure, Function and Utilization of Plant Photosynthetic Reaction Centers. United States Department of Agriculture, September 2012. http://dx.doi.org/10.32747/2012.7699846.bard.
Full textAbstract:
Light capturing and energy conversion by PSI is one of the most fundamental processes in nature. In the heart of these adaptations stand PSI, PSII and their light harvesting antenna complexes. The main goal of this grant proposal was to obtain by X-ray crystallography information on the structure of plant photosystem I (PSI) and photosystem II (PSII) supercomplexes. We achieved several milestones along this line but as yet, like several strong laboratories around the world, we have no crystal structure of plant PSII. We have redesigned the purification and crystallization procedures and recently solved the crystal structure of the PSI supercomplex at 3.3 Å resolution. Even though this advance in resolution appears to be relatively small, we obtained a significantly improved model of the supercomplex. The work was published in J. Biol. Chem. (Amunts et al., 2010). The improved electron density map yielded identification and tracing of the PsaK subunit. The location of an additional 10 ß-carotenes, as well as 5 chlorophylls and several loop regions that were previously uninterruptable have been modeled. This represents the most complete plant PSI structure obtained thus far, revealing the locations of and interactions among 17 protein subunits and 193 non-covalently bound photochemical cofactors. We have continued extensive experimental efforts to improve the structure of plant PSI and to obtain PSII preparation amenable to crystallization. Most of our efforts were devoted to obtain well-defined subcomplexes of plant PSII preparations that are amenable to crystallization. We studied the apparent paradox of the high sensitivity of oxygen evolution of isolated thylakoids while BBY particles exhibit remarkable resilience to the same treatment. The integrity of the photosystem II (PSII) extrinsic protein complement as well as calcium effects arise from the Ca2+ atom associated with the site of photosynthetic water oxidation were investigated. This work provides deeper insights into the interaction of PsbO with PSII. Sight-directed mutagenesis indicated the location of critical sites involved in the stability of the water oxidation reaction. When combined with previous results, the data lead to a more detailed model for PsbO binding in eukaryotic PSII.