Conserved features in papillomavirus and polyomavirus capsids
Abstract
Papovaviruses are non-enveloped viruses that have been observed primarily in humans and other mammals. The family Papovaviridae includes the genus Papillomavirus (e.g. bovine, cottontail rabbit, and human papillomaviruses) and the genus Polyomavirus (e.g. murine polyomavirus and simian virus 40). Papillomavirus and polyomavirus capsids are composed of 72 pentameric capsomeres arranged on a skewed icosahedral lattice (triangulation number of seven, T = 7). Cottontail rabbit papillomavirus (CRPV) was reported previously to be a T = 7laevo (left-handed) structure, whereas human wart virus, simian virus 40, and murine polyomavirus were shown to be T = 7dextro (right-handed). The CRPV structure determined by cryoelectron microscopy and image reconstruction was similar to previously determined structures of bovine papillomavirus type 1 (BPV-1) and human papillomavirus type 1 (HPV-1). Papillomavirus capsids were observed in compact and swollen forms. The lattice hands of BPV-1, CRPV, and HPV-1 were found to be T = 7dextro. In the region of maximum contact, papillomavirus capsomeres interact in a manner similar to that found in polyomaviruses. An alignment of 68 amino acid sequences from papillomavirus and polyomavirus major capsid proteins indicates that several residues are conserved in potentially significant places, including a proposed calcium-binding site. A fit of the high-resolution structure of murine polyomavirus into the relatively low-resolution HPV-1 reconstruction suggests that papillomaviruses have a similar core structure. Although papilloma and polyoma viruses have differences in capsid size, capsomere morphology, and intercapsomere interactions, papovavirus capsids have a conserved, 72-pentamer, T = 7dextro structure. These features are conserved despite significant differences in amino-acid sequences of the major capsid proteins. The conserved features may be a consequence of stable contacts that occur within capsomeres and flexible links that form among capsomeres.
Degree
Ph.D.
Advisors
Baker, Purdue University.
Subject Area
Biophysics|Microbiology|Molecular biology
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