Crystallization and preliminary crystallographic analysis of San Miguel sea lion virus: an animal calicivirus

Abstract

The Caliciviridae is a family of nonenveloped, icosahedral, positive-sense single-stranded RNA viruses. This family of viruses consists of both animal and human pathogens. Adapting human caliciviruses to cell culture has not been successful, whereas some animal caliciviruses, including San Miguel sea lion virus, have been successfully propagated in vitro. Here we report the crystallization of San Miguel sea lion virus serotype 4 (SMSV4) and the preliminary X-ray crystallographic analysis of the crystals. SMSV4 have been crystallized using the hanging-drop method. These crystals diffracted to approximately 3A resolution using a synchrotron radiation source. A single crystal under cryo-conditions yielded a complete set of diffraction data. Data processing of the diffraction patterns showed that SMSV crystals belong to I23 space group with cell dimensions a=b=c=457 A. The crystallographic asymmetric unit includes five icosahedral asymmetric units, each consisting of three capsid protein subunits. In the space group I23, given the icosahedral symmetry and the size of the virus particle, the location of the particle is constrained to be at the point where the crystallographic 2- and 3-fold axes intersect. The orientation of the virus particle in the unit cell was ascertained by self-rotation function calculations.