Classification of capped tubular viral particles in the family of Papovaviridae

Abstract

A vital constituent of a virus is its protein shell, called the viral capsid, that encapsulatesand hence provides protection for the viral genome. Viral capsids are usually spherical, andfor a significant number of viruses they exhibit overall icosahedral symmetry. Thecorresponding surface lattices, that encode the locations of the capsid proteins andintersubunit bonds, can be modelled by viral tiling theory. It has been shown in vitro thatunder a variation of the experimental boundary conditions, such as the pH valueand salt concentration, tubular particles may appear instead of, or in additionto, spherical ones. In order to develop models that describe the simultaneousassembly of both spherical and tubular variants, and hence study the possibility oftriggering tubular malformations as a means of interference with the replicationmechanism, viral tiling theory has to be extended to include tubular lattices with endcaps. We focus here on the case of Papovaviridae, which play a distinguishedrole from the viral structural point of view as they correspond to all pentamerlattices, i.e. lattices formed from clusters of five protein subunits throughout. Theseresults pave the way for a generalization of recently developed assembly models.