Purification, crystallization and preliminary X-ray structural studies of a 7.2 kDa cytotoxin isolated from the venom of Daboia russelli russelli of the Viperidae family

A cytotoxin (MW 7.2 kDa) from Indian Russell's viper (Daboia russelli russelli) venom possessing antiproliferative activity, cardiotoxicity, neurotoxicity and myotoxicity has been purified, characterized and crystallized. The crystals belong to the tetragonal space group P4₁, with unit-cell parameters a = b = 47.94, c = 50.2 Å. Larger crystals, which diffracted to 1.5 Å, were found to be twinned; diffraction data were therefore collected to 2.93 Å resolution using a smaller crystal. Molecular-replacement calculations identified two molecules of the protein in the asymmetric unit, which is in accordance with the calculated V_M value.