The crystal structure of a lysine 49 phospholipase A sub(2) from the venom of the cottonmouth snake at 2.0-angstrom resolution

The crystal structure of a lysine 49 variant phospholipase A sub(2) (K49 PAL2) has been determined at 2.0-angstroms resolution. This particular phospholipase A sub(2), purified from the venom of the eastern cottonmouth (Agkistrodon piscivorus piscivorus)), a North American pit viper, differs significantly from others studied crystallographically because of replacement of the aspartate residue at position 49, whose side chain is important in calcium binding, by lysine. The K49 PLA2 model is composed primarily of alpha -helices joined by loops, some of which are quite extensive. Although dissimilarities are observed in the loop regions, the helical portions are very similar to those in other known phospholipase A sub(2) structures.