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Determination of the disulfide bridges in factor Va light chain
1Department of Biochemistry, University of Vermont, Burlington 05405-0068.
Abstract:
The 74-kDa light chain of bovine factor Va is composed of three domains: the NH2-terminal A3 domain and the COOH-terminal C1 and C2 domains. In total, the light chain has eight cysteines: two in the A3 domain and three in each C domain. To determine the locations of the disulfide bridges, peptides were obtained from factor Va and iodo[1-14C]acetamide-labeled factor Va light chains by digestion with trypsin, activated protein C, lysylendopeptidase, and V8 protease. After HPLC purification, amino acid sequence and composition analyses showed that each domain of bovine Va light chain possesses a disulfide bond. The sites are Cys1684-Cys1710 (A3), Cys1866-Cys2020 (C1), and Cys2025-Cys2180 (C2). One free cysteine is located in each C domain, i.e., Cys1953 and Cys2100. The locations of the disulfide bonds in human Va and VIIIa light chains are anticipated to be similar to those of bovine Va light chain, because the cysteines involved are conserved.