The Refined Structure of a Protein Catenane: The Hk97 Bacteriophage Capsid at 3.44A ResolutionHelgstrand, C., Wikoff, W.R., Duda, R.L., Hendrix, R.W., Johnson, J.E., Liljas, L.
(2003) J.Mol.Biol. 334: 885
- PubMed: 14643655
- PubMed Abstract:
- Topologically Linked Protein Rings in the Bacteriophage Hk97 Capsid
Wikoff, W.R.,Liljas, L.,Duda, R.L.,Tsuruta, H.,Hendrix, R.W.,Johnson, J.E.
(2000) Science 289: 2129
- Increased Resolution Data from a Large Unit Cell Crystal Collected at a Third-Generation Synchrotron X-Ray Source
Wikoff, W.R.,Schildkamp, W.,Johnson, J.E.
(2000) Acta Crystallogr.,Sect.D 56: 890
- Crystallographic Analysis of the DsDNA Bacteriophage Hk97 Mature Empty Capsid
Wikoff, W.R.,Duda, R.L.,Hendrix, R.W.,Johnson, J.E.
(1999) Acta Crystallogr.,Sect.D 55: 763
The HK97 bacteriophage capsid is a unique example of macromolecular catenanes: interlocked rings of covalently attached protein subunits. The chain mail organization of the subunits stabilizes a particle in which the maximum thickness of the protein ...
The HK97 bacteriophage capsid is a unique example of macromolecular catenanes: interlocked rings of covalently attached protein subunits. The chain mail organization of the subunits stabilizes a particle in which the maximum thickness of the protein shell is 18A and the maximum diameter is 550A. The electron density has the appearance of a balloon illustrating the extraordinary strength conferred by the unique subunit organization. The refined structure shows novel qualities of the HK97 shell protein, gp5 that, together with the protease gp4, guides the assembly and maturation of the virion. Although gp5 forms hexamers and pentamers and the subunits exist in different structural environments, the tertiary structures of the seven protein molecules in the viral asymmetric unit are closely similar. The interactions of the subunits in the shell are exceptionally complex with each subunit interacting with nine other subunits. The interactions of the N-terminus released after gp5 cleavage appear important for organization of the loops that become crosslinked to the core of a neighboring subunit at the maturation. A comparison with a model of the Prohead II structure revealed that the surfaces of non-covalent contact between the monomers that build up hexamers/pentamers are completely redefined during maturation.
Department of Cell and Molecular Biology, Uppsala University, Box 596, 75124 Uppsala, Sweden.