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J Mol Biol. 2006 Sep 1;361(5):993-1002. Epub 2006 Jul 31.

Bacteriophage T5 structure reveals similarities with HK97 and T4 suggesting evolutionary relationships.

Author information

1
Laboratoire de Microscopie Electronique Structurale, Institut de Biologie Structurale J.-P. Ebel, UMR 5075 CNRS-CEA-UJF, 38027 Grenoble, France.

Abstract

Evolutionary relationships between viruses may be obscure by protein sequence but unmasked by structure. Analysis of bacteriophage T5 by cryo-electron microscopy and protein sequence analysis reveals analogies with HK97 and T4 that suggest a mosaic of such connections. The T5 capsid is consistent with the HK97 capsid protein fold but has a different geometry, incorporating three additional hexamers on each icosahedral facet. Similarly to HK97, the T5 major capsid protein has an N-terminal extension, or Delta-domain that is missing in the mature capsid, and by analogy with HK97, may function as an assembly or scaffold domain. This Delta-domain is predicted to be largely coiled-coil, as for that of HK97, but is approximately 70% longer correlating with the larger capsid. Thus, capsid architecture appears likely to be specified by the Delta-domain. Unlike HK97, the T5 capsid binds a decoration protein in the center of each hexamer similarly to the "hoc" protein of phage T4, suggesting a common role for these molecules. The tail-tube has unusual trimeric symmetry that may aid in the unique two-stage DNA-ejection process, and joins the tail-tip at a disk where tail fibers attach. This intriguing mix of characteristics embodied by phage T5 offers insights into virus assembly, subunit function, and the evolutionary connections between related viruses.

PMID:
16876823
DOI:
10.1016/j.jmb.2006.06.081
[Indexed for MEDLINE]

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