Characterization, crystallization and preliminary X-­ray diffraction analysis of acutohaemolysin, a haemolytic toxin from Agkistrodon acutus venom

Acutohaemolysin, a phospholipase A₂ (PLA₂) from the venom of the snake Agkistrodon acutus, has been isolated and purified to homogeneity by anion-exchange chromatography on a DEAE–Sepharose column followed by cation-exchange chromatography on a CM–Sepharose column. It is an alkaline protein with an isoelectric point of 10.5 and is comprised of a single polypeptide chain of 13 938 Da. Its N-terminal amino-acid sequence shows very high similarity to Lys49-type PLA₂ proteins from other snake venoms. Although its PLA₂ enzymatic activity is very low, acutohaemolysin has a strong indirect haemolytic activity and anticoagulant activity. Acutohaemolysin crystals with a diffraction limit of 1.60 Å were obtained by the hanging-drop vapour-diffusion method. The crystals belong to the space group C2, with unit-cell parameters a = 45.30, b = 59.55, c = 46.13 Å, β = 117.69°. The asymmetric unit contains one molecule.