PubMed · 1438848
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S Koike. 1992. [Picornavirus receptor].. https://pubmed.ncbi.nlm.nih.gov/1438848/
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Genome replication in picornaviruses is catalyzed by a virally encoded RNA-dependent RNA polymerase, termed 3D. These viruses also use a small protein primer, named VPg, to initiate RNA replication. The recent explosion of structural information on picornaviral 3D polymerases has provided insights into the initiation of RNA synthesis and chain elongation. Comparing these data with results from previous structural analyses of viral RNA-dependent RNA polymerases that catalyze de novo RNA synthesis sheds light on the different strategies that these viruses use to initiate replication.
The surface topology and sequence conservation of different picornaviruses have been compared using molecular graphics and statistical analyses. The comparisons suggest that the canyons, surface depressions encircling the fivefold axes, are the sites of receptor attachment of enteroviruses as well as human rhinovirus (HRV). In HRV14, the receptor binding footprint extends beyond the canyon (Olson et al. (1993), Proc. Natl. Acad. Sci. USA 90, 507-511), but these more exposed regions are not conserved in polioviruses or minor receptor group rhinoviruses, suggesting some differences in receptor binding. When rhinoviruses are compared to other picorna- and parvoviruses, the surface sequence similarity relative to the similarity of buried residues is about the same. Thus, the effect of host immune surveillance on surface residues is similar. Therefore, it is probable that some means of protecting a conserved binding site from immune detection (such as a canyon) will be an essential requirement in other viruses. However, there may be other strategies for achieving this result. For instance, as in foot-and-mouth disease virus, the receptor attachment site of Mengo virus is associated with a flexible structural component which may inhibit the production of neutralizing antibodies that are able to recognize only one explicit conformation.
Sequence comparisons reveal that positive-strand RNA viruses not only evolve by divergence from common ancestors but also by interviral recombination. A considerable number of these viruses, exemplified by the family Potyviridae, can in fact, be regarded as successful products of a number of recombination events. It is concluded that the recombinative character of RNA viruses will hamper any attempt to set up a true phylogenetic taxonomy. It is advisable, therefore, to avoid the introduction of any taxon higher-than-family in virus taxonomy.