A monoclonal antibody recognizing the activation domain of protein C in its calcium-free conformation.
A monoclonal antibody (mAb) binding to protein C (PC) heavy chain but not to activated PC was found to inhibit PC activation by free thrombin, suggesting that epitope involved the activation site. Using a set of overlapping synthetic peptides, we confirmed that this mAb recognizes the sequence encompassing the thrombin cleavage site (165QVDPRLI(171)). Surprisingly, epitope was only accessible in the absence of calcium, half-maximal inhibition of mAb binding occurring at 100 microM Ca2+. Thus, our antibody provides direct evidence that conformation and/or accessibility of the activation site differ between the apo and Ca2+-stabilized conformers of PC.
Vincenot
A
A
INSERM U 428, Faculté de Pharmacie, Paris, France.
Pittet
J L
JL
Aiach
M
M
Gaussem
P
P
D000818:Animals; D000911:Antibodies, Monoclonal; D000918:Antibody Specificity / Q000187:drug effects*; D002118:Calcium / Q000494:pharmacology*; D004789:Enzyme Activation; D018604:Epitope Mapping; D000939:Epitopes; D006801:Humans; D051379:Mice; D011486:Protein C / Q000276:immunology*; D011487:Protein Conformation
D000911:Antibodies, Monoclonal; D000939:Epitopes; D011486:Protein C; D002118:Calcium