Crystallization and preliminary X-ray diffraction analysis of three myotoxic phospholipases A₂ from Bothrops brazili venom

Two myotoxic and noncatalytic Lys49-phospholipases A₂ (braziliantoxin-II and MT-II) and a myotoxic and catalytic phospholipase A₂ (braziliantoxin-III) from the venom of the Amazonian snake Bothrops brazili were crystallized. The crystals diffracted to resolutions in the range 2.56-2.05 Å and belonged to space groups P3₁21 (braziliantoxin-II), P6₅22 (braziliantoxin-III) and P2₁ (MT-II). The structures were solved by molecular-replacement techniques. Both of the Lys49-phospholipases A₂ (braziliantoxin-II and MT-II) contained a dimer in the asymmetric unit, while the Asp49-phospholipase A₂ braziliantoxin-III contained a monomer in its asymmetric unit. Analysis of the quaternary assemblies of the braziliantoxin-II and MT-II structures using the PISA program indicated that both models have a dimeric conformation in solution. The same analysis of the braziliantoxin-III structure indicated that this protein does not dimerize in solution and probably acts as a monomer in vivo, similar to other snake-venom Asp49-phospholipases A₂.