National Laboratory of Biomacromolecules, Academia Sinica, Beijing, China.
The crystal structure of acidic phospholipase A2 from the venom of Agkistrodon halys pallas has been determined by molecular replacement at 2.0 A resolution to a crystallographic R-factor of 0.157. The overall structure of the molecule is very similar to those of other phospholipase A2 species of known structure. The catalytic site, the hydrophobic channel and the N-terminal region show greatest structural conservation. The Ca(2+)-binding region has a conformation that resembles closely that of bovine PLA2 rather than Crotalus atrox PLA2. Compared with other PLA2 species, the conformation of the C-terminal ridge shows significant difference due to the insertion of two residues. A unique aromatic patch appears on one face of the molecules, surrounded by two acidic residues, the relevant features of this structure and their possible biological implications are discussed.