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02.066.0.01.002. Enterobacteriophage HK97
EM provided by ICTV Study Group for bacterial viruses.


HK97 assembly and maturation. (A) Negatively stained electron micrograph of a mature dsDNA-filled capsid, with noncontractile tail and accessory proteins. (B) Steps in capsid assembly and maturation (see text; in vitro conditions are in bold, and in vivo conditions or components that differ from the in vitro conditions are in italic) (9). (C) Chemistry of the cross-linking reaction.

Wikoff WR, Liljas L, Duda RL, Tsuruta H, Hendrix RW, Johnson JE. (2000) Topologically linked protein rings in the bacteriophage HK97 capsid. Science. 2000 Sep 22;289(5487):2129-33.

Department of Molecular Biology, Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.

The crystal structure of the double-stranded DNA bacteriophage HK97 mature empty capsid was determined at 3.6 angstrom resolution. The 660 angstrom diameter icosahedral particle contains 420 subunits with a new fold. The final capsid maturation step is an autocatalytic reaction that creates 420 isopeptide bonds between proteins. Each subunit is joined to two of its neighbors by ligation of the side-chain lysine 169 to asparagine 356. This generates 12 pentameric and 60 hexameric rings of covalently joined subunits that loop through each other, creating protein chainmail: topologically linked protein catenanes arranged with icosahedral symmetry. Catenanes have not been previously observed in proteins and provide a stabilization mechanism for the very thin HK97 capsid.



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International Committee on Taxonomy of Viruses  2002 All rights reserved.
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