Calcium ion binding to human and bovine factor X.

D. M. Monroe, D. W. Deerfield, D. L. Olson, T. N. Stewart, R. E. Treanor, H. R. Roberts, R. G. Hiskey, L. G. Pedersen

Research output: Contribution to journalArticlepeer-review

Abstract

Human and bovine factor X contain 11 and 12 glutamyl residues, respectively, within the first 40 amino terminal residues that are post-translationally modified to gamma-carboxyglutamyl (Gla) residues. We have measured calcium ion binding to human factor X by equilibrium dialysis. This is the first examination of calcium ion binding to human factor X. We have also re-examined the equilibrium dialysis binding of calcium ions to bovine facor X in order to compare the two species. The data was analysed using a variety of models that allow for more than one class of binding site and for co-operativity among binding sites. Calcium ion binding to human factor X fits a model that had two classes of sites: one class with a single site that had an affinity of 0.1 mM and a second class with 19 equivalent, non-interacting sites with an average affinity of 3.5 mM. There was no evidence for co-operativity in calcium ion binding. Calcium ion binding to bovine factor X was best stimulated by a model that assumed one tight site, four co-operative sites, and 18 equivalent, non-interacting sites. To examine the co-operativity seen in calcium ion binding to bovine factor X, calcium ion binding to isolated Gla region (residues 1-44) and Gla-domainless factor X was measured by equilibrium dialysis. Calcium ion binding to Gla-domainless factor X was simulated by a model that had two classes of sites: one class with a single site that had an affinity of 0.25 mM, and a second class that had 15 sites with very low affinity sites (greater than 15 mM).(ABSTRACT TRUNCATED AT 250 WORDS)

Original languageEnglish (US)
Pages (from-to)633-640
Number of pages8
JournalBlood coagulation & fibrinolysis : an international journal in haemostasis and thrombosis
Volume1
Issue number6
StatePublished - Dec 1990
Externally publishedYes

ASJC Scopus subject areas

  • Hematology

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