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Acidic phospholipase A₂ (PLA₂) isoforms in snake venoms, particularly those from Bothrops jararacussu, have not been characterized. This article reports the isolation and partial biochemical, functional and structural characterization of four acidic PLA₂s (designated SIIISPIIA, SIIISPIIB, SIIISPIIIA and SIIISPIIIB) from this venom. The single chain purified proteins contained 122 amino acid residues and seven disulfide bonds with approximate molecular masses of 15 kDa and isoelectric points of 5.3. The respective N-terminal sequences were: SIIISPIIA–SLWQFGKMIDYVMGEEGAKS; SIIISPIIB–SLWQFGKMIFYTGKNEPVLS; SIIISPIIIA–SLWQFGKMILYVMGGEGVKQ and SIIISPIIIB–SLWQFGKMIFYEMTGEGVL. Crystals of the acidic protein SIIISPIIB diffracted beyond 1.8 Å resolution. These crystals are monoclinic with unit cell dimensions of a = 40.1 Å, b = 54.2 Å and c = 90.7 Å. The crystal structure has been refined to …