title: Secondary substrate-binding exosite in the serine protease domain of activated protein C important for cleavage at Arg-506 but not at Arg-306 in factor Va.
abstract: Proteolytic inactivation of activated factor V (FVa) by activated protein C (APC) is a key reaction in the regulation of hemostasis. We now demonstrate the importance of a positive cluster in loop 37 of the serine protease (SP) domain of APC for the degradation of FVa. Lysine residues in APC at positions 37, 38, and 39 form a secondary binding site for FVa, which is important for cleavage of FVa at Arg-506 while having no effect on Arg-306 cleavage. In contrast, topological neighbors Lys-62, Lys-63, and Arg-74 in APC appear of minor importance in FVa degradation. This demonstrates that secondary binding exosites of APC specifically guide the proteolytic action of APC, resulting in a more favorable degradation of the 506-507 peptide bond as compared with the 306-307 bond.
authors: Department of Clinical Chemistry, Lund University, The Wallenberg Laboratory, MAS, SE-205 02 Malmö, Sweden.
authors: U
authors: U
authors: Friedrich
authors: G A
authors: GA
authors: Nicolaes
authors: B O
authors: BO
authors: Villoutreix
authors: B
authors: B
authors: Dahlbäck
mesh_terms: D001120:Arginine / Q000378:metabolism*; D001665:Binding Sites; D002384:Catalysis; D015943:Factor Va / Q000378:metabolism*; D006801:Humans; D006868:Hydrolysis; D007700:Kinetics; D011486:Protein C / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012697:Serine Endopeptidases / Q000737:chemistry / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D011486:Protein C; D011994:Recombinant Proteins; D015943:Factor Va; D001120:Arginine; D012697:Serine Endopeptidases