title: Topologically linked protein rings in the bacteriophage HK97 capsid.
abstract: 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.
authors.affiliation: Department of Molecular Biology, Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
authors.forename: W R
authors.initials: WR
authors.lastname: Wikoff
authors.forename: L
authors.initials: L
authors.lastname: Liljas
authors.forename: R L
authors.initials: RL
authors.lastname: Duda
authors.forename: H
authors.initials: H
authors.lastname: Tsuruta
authors.forename: R W
authors.initials: RW
authors.lastname: Hendrix
authors.forename: J E
authors.initials: JE
authors.lastname: Johnson
mesh_terms: D001216:Asparagine / Q000737:chemistry / Q000378:metabolism; D002213:Capsid / Q000737:chemistry* / Q000378:metabolism; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008239:Lysine / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D011487:Protein Conformation; D017510:Protein Folding; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D017906:Siphoviridae / Q000737:chemistry* / Q000378:metabolism
chemical_list: D001216:Asparagine; D008239:Lysine