부산대학교 도서관

α-Type phospholipase A2 inhibitory protein (PLIα) from the serum of the venomous snake Gloydius brevicaudus, GbPLIα, is one of the protective endogenous proteins that neutralizes its own venom phospholipase Aβ (PLA2), and it is a homotrimer of subunits having a C-type lectin-like domain. The nonvenomous snake Elaphe quadrivirgata has a homologous serum protein, EqPLIα-LP, that does not show any inhibitory activity against various snake venom PLA2s (Okumura, K., Inoue, S., Ikeda, K., and Hayashi, K. (2003) IUBMB Life 55, 539–545). By constructing GbPLIα-Eq-PLIα-LP chimeric proteins, we have mapped the residues important in conferring GbPLIα inhibitory activity on region 13–36 in the primary structure of GbPLIα. Noninhibitory EqPLIα-LP showed comparable inhibitory activity only when this region was replaced with that of GbPLIα. Further, mutational analysis of the candidate residues revealed that the individual GbPLIα to EqPLIα-LP residue substitutions N26K, K28E, D29N, and Y144S each produced a mutant GbPLIα protein with reduced inhibitory activity, with the single N26K substitution having the most significant effect. Residues 13–36 were suspected to be located in the helical neck region of the GbPLIα trimer. Therefore, the region of GbPLIα responsible for PLAβ inhibition was distinct from the carbohydrate-binding site of the homologous C-type lectin. [ABSTRACT FROM AUTHOR]