Amino acids 225-235** of the protein C serine-protease domain are important for the interaction with the thrombin-thrombomodulin complex.
Protein C (PC) is a vitamin K-dependent zymogen that inactivates factors Va and VIIIa after its activation by thrombin complexed to thrombomodulin. We characterized a monoclonal antibody (mAb) against PC, whose only influence on PC functions was to inhibit PC activation by the thrombin-thrombomodulin complex. It recognized an epitope in the PC heavy chain, the conformation of which is calcium-dependent. The mAb did not recognize a natural PC variant that was not activated by the thrombin-thrombomodulin complex (mutation R229Q) and did recognize a synthetic peptide corresponding to PC amino acids 225-235 in an Elisa assay. The peptide inhibited PC activation by the thrombin-thrombomodulin complex. These data confirm that the calcium-binding loop of the serine-protease domain is involved in the interaction of PC with the thrombin-thrombomodulin complex.
Vincenot
A
A
INSERM U428, UFR des Sciences Pharmaceutiques et Biologiques, Université Paris V, France.
Gaussem
P
P
Pittet
J L
JL
Debost
S
S
Aiach
M
M
D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal; D002118:Calcium / Q000378:metabolism; D004789:Enzyme Activation; D000939:Epitopes / Q000276:immunology; D006579:Heterozygote; D006801:Humans; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000494:pharmacology; D011486:Protein C / Q000737:chemistry* / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D011487:Protein Conformation; D013917:Thrombin / Q000378:metabolism*; D018180:Thrombomodulin / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D000939:Epitopes; D009842:Oligopeptides; D011486:Protein C; D018180:Thrombomodulin; D013917:Thrombin; D002118:Calcium