Purification, crystallization and preliminary X-ray diffraction analysis of an acidic phospholipase A₂ with vasoconstrictor activity from Agkistrodon halys pallas venom

Phospholipases A₂ (PLA₂s) are the major component of snake venoms and exert a variety of relevant toxic actions such as neurotoxicity and myotoxicity, amongst others. An acidic PLA₂, here named AhV_aPA, was purified from Agkistrodon halys pallas venom by means of a three-step chromatographic procedure. AhV_aPA migrated as a single band on SDS-PAGE gels, with a molecular weight of about 14 kDa. Like other acidic aPLA₂s, AhV_aPA has high enzymatic activity. Tension measurements of mouse thoracic aortic rings remarkably indicated that AhV_aPA could induce a further contractile response on the 60 mM K⁺-induced contraction, with an EC₅₀ of 369 nmol l^-1. Rod-shaped crystals were obtained by the hanging-drop vapour-diffusion method and diffracted to a resolution limit of 2.30 Å. The crystals belonged to space group P222, with unit-cell parameters a = 44.27, b = 68.39, c = 81.54 Å.