Coxsackievirus B3 Protease 3C: Expression, Purification, Crystallization and Preliminary Structural Insights.

Viral proteases are proteolytic enzymes that orchestrate the assembly of viral components during the viral life cycle and proliferation. Here, the expression, purification, crystallization and preliminary X-ray diffraction analysis are presented of protease 3C, the main protease of an emerging enterovirus, coxsackievirus B3, that is responsible for many cases of viral myocarditis. Polycrystalline protein precipitates suitable for X-ray powder diffraction (XRPD) measurements were produced in the presence of 22–28%(w/v) PEG 4000, 0.1 MTris–HCl, 0.2 MMgCl2in a pH range from 7.0 to 8.5. A polymorph of monoclinic symmetry (space groupC2, unit-cell parametersa = 77.9,b= 65.7,c = 40.6 Å, β = 115.9°) was identifiedviaXRPD. These results are the first step towards the complete structural determination of the moleculeviaXRPD and a parallel demonstration of the accuracy of the method.