Purification, crystallization and preliminary X‐ray diffraction analysis of saxthrombin, a thrombin‐like enzyme from Gloydius saxatilis venom
The snake‐venom thrombin‐like enzymes (SVTLEs) are a class of serine proteinases that show fibrinogen‐clotting and esterolytic activities. Most TLEs convert fibrinogen to fibrin by releasing either fibrinopeptide A or fibrinopeptide B and cannot activate factor XIII. The enzymes hydrolyze fibrinogen to produce non‐cross‐linked fibrins, which are susceptible to the lytic action of plasmin. Because of these physiological properties, TLEs have important medical applications in myocardial infarction, ischaemic stroke and thrombotic diseases. Here, a three‐step chromatography procedure was used to purify saxthrombin (AAP20638) from Gloydius saxatilis venom to homogeneity. Its molecular weight is about 30 kDa as estimated by SDS–PAGE. A saxthrombin crystal was obtained using the hanging‐drop vapour‐diffusion method and diffracted to a resolution limit of 1.43 Å. The crystal belongs to space group C2, with unit‐cell parameters a = 97.23, b = 52.21, c = 50.10 Å, β = 96.72°, and the Matthews coefficient (V M) was calculated to be 2.13 Å3 Da−1 with one molecule in the asymmetric unit.
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