title: The propeptides of the vitamin K-dependent proteins possess different affinities for the vitamin K-dependent carboxylase.
abstract: The vitamin K-dependent gamma-glutamyl carboxylase catalyzes the modification of specific glutamates in a number of proteins required for blood coagulation and associated with bone and calcium homeostasis. All known vitamin K-dependent proteins possess a conserved eighteen-amino acid propeptide sequence that is the primary binding site for the carboxylase. We compared the relative affinities of synthetic propeptides of nine human vitamin K-dependent proteins by determining the inhibition constants (Ki) toward a factor IX propeptide/gamma-carboxyglutamic acid domain substrate. The Ki values for six of the propeptides (factor X, matrix Gla protein, factor VII, factor IX, PRGP1, and protein S) were between 2-35 nM, with the factor X propeptide having the tightest affinity. In contrast, the inhibition constants for the propeptides of prothrombin and protein C are approximately 100-fold weaker than the factor X propeptide. The propeptide of bone Gla protein demonstrates severely impaired carboxylase binding with an inhibition constant of at least 200,000-fold weaker than the factor X propeptide. This study demonstrates that the affinities of the propeptides of the vitamin K-dependent proteins vary over a considerable range; this may have important physiological consequences in the levels of vitamin K-dependent proteins and the biochemical mechanism by which these substrates are modified by the carboxylase.
authors.affiliation: Department of Biology, Center for Thrombosis and Hemostasis, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3280, USA.
authors.forename: T B
authors.initials: TB
authors.lastname: Stanley
authors.forename: D Y
authors.initials: DY
authors.lastname: Jin
authors.forename: P J
authors.initials: PJ
authors.lastname: Lin
authors.forename: D W
authors.initials: DW
authors.lastname: Stafford
mesh_terms: D000595:Amino Acid Sequence; D001777:Blood Coagulation; D001779:Blood Coagulation Factors / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism; D019735:Carbon-Carbon Ligases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D017124:Conserved Sequence; D016326:Extracellular Matrix Proteins; D005164:Factor IX / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D011498:Protein Precursors / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D017293:Protein S / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D014812:Vitamin K / Q000378:metabolism*; D000097568:Matrix Gla Protein
chemical_list: D001779:Blood Coagulation Factors; D002118:Calcium; D002135:Calcium-Binding Proteins; D019735:Carbon-Carbon Ligases; D016326:Extracellular Matrix Proteins; D005164:Factor IX; D011498:Protein Precursors; D017293:Protein S; D011994:Recombinant Proteins; D014812:Vitamin K; D000097568:Matrix Gla Protein; C049838:factor IX Cambridge; C020660:glutamyl carboxylase