cDNA cloning of IX/X-BP, a heterogeneous two-chain anticoagulant protein from snake venom.

IX/X-bp is an anticoagulant protein isolated from the venom of the habu snake (Trimeresurus flavoviridis). It is a heterogeneous two-chain protein linked by an interchain S-S bond. We prepared a cDNA library from the venom gland of the habu snake in the vector pSPORT1. cDNA clones containing the coding sequences for IX/X-bp were isolated and sequenced to determine the structure of the proprotein of IX/X-bp. All cDNA clones containing coding sequences of either chain of IX/X-bp consisted of the 5'-end noncoding bases, the first ATG codon, a typical signal peptide sequence that was immediately followed by mature protein sequence that corresponded to one of the chains, a stop codon, the 3'-end noncoding bases, a polyadenylation signal, and a poly(A)+ region. These data indicate that the gene for each chain of the two-chain protein is transcribed and translated separately.