Structural elements of Trimeresurus flavoviridis serum inhibitors for recognition of its venom phospholipase A2 isozymes

Fire inhibitors (PLI-I-V) against Trimeresurus flavoviridis (Tf, habu snake, Crotalinae) venom phospholipase A(2) (PLA(2)) isozymes have been isolated from its serum. PLI-I, which is composed of two repeated three-finger motifs, and PLI-IV and PLI-V, which contain a sequence similar to the carbohydrate recognition domain (CRD) of C-type lectins, mere er;pressed in the forms fused with glutathione S-transferase (GST), The resulting GST-PLIs showed ability to bind to three Tf venom PLA2 isozymes, The binding study with the truncated forms indicated that one of tno three-finger motifs of PLI-I was able to bind to PLA(2) isozymes, The N-terminal 37-amino acid fragment and the CRD-like domain of PLI-IV and PLI-V mere bound to PLA(2) isozymes. On the other hand, their C-terminal 12-amino acid segment also associated,vith PLA2 isozymes. When either of two units of a hydrophobic tripeptide in this sequence was replaced by trialanine, the binding was completely abolished, indicating that the C-terminal hydrophobic cores of PLI-IV and PLI-V mere critically responsible for the binding to venom PLA(2) isozymes. (C) 1998 Federation of European Biochemical Societies.