Amino acid sequence of a basic aspartate-49-phospholipase A 2 from Trimeresurus flavoviridis venom and phylogenetic analysis of Crotalinae venom phospholipases A 2

Abstract

Trimeresurus flavoviridis snakes inhabit the southwestern islands of Japan: Amami-Oshima, Tokunoshima and Okinawa. A phospholipase A 2 (PLA 2) of basic nature (pI 8.5) was isolated from the venom of Amami-Oshima T. flavoviridis. Its amino acid sequence determined by the ordinary procedures was completely in accord with that predicted from the nucleotide sequence of the cDNA previously cloned from Amami-Oshima T. flavoviridis venom gland, which was named PLA-B′. It consists of 122 amino acid residues and has aspartate at position 49. It induced edema in a mouse footpad assay and caused necrosis in mouse skeletal muscles. PLA-B′ is similar in sequence to PLA-B (Tokunoshima) and PL-Y (Okinawa), both basic [Asp 49]PLA 2s, with a few amino acid substitutions, indicating occurrence of interisland mutation. Although PLA 2s of Crotalinae subfamily were phylogenetically classified into four types, PLA2 (acidic or neutral [Asp 49]PLA 2) type, basic [Asp 49]PLA 2 type, neurotoxic [Asp 49]PLA 2 type and [Lys 49]PLA 2 type, it was ascertained that PLA 2s of PLA2 type and [Lys 49]PLA 2 type are most essential as toxic components for Crotalinae snake venoms and that basic [Asp 49]PLA 2-type PLA 2s are uniquely contained only in the venoms of T. flavoviridis species. Prediction of physiological activities of some PLA 2s was made based on their location in the phylogenetic tree. Relationship of divergence of PLA 2s via accelerated evolution followed by less rapid mutation and physiological activities was discussed.