The Structure of Bacteriophage phi Cb5 Reveals a Role of the RNA Genome and Metal Ions in Particle Stability and Assembly
2009 (English)In: Journal of Molecular Biology, ISSN 0022-2836, E-ISSN 1089-8638, Vol. 391, no 3, 635-647 p.Article in journal (Refereed) Published
The structure of the Leviviridae bacteriophage φCb5 virus-like particle has been determined at 2.9Å resolution and the structure of the native bacteriophage φCb5 at 3.6Å. The structures of the coat protein shell appear identical while differences are found in the organization of the density corresponding to the RNA. The capsid is built of coat protein dimers and in shape corresponds to a truncated icosahedron with T=3 quasi-symmetry. The capsid is stabilized by four calcium ions per icosahedral asymmetric unit. One is located at the symmetry axis relating the quasi-threefold related subunits and is part of an elaborate network of hydrogen bonds stabilizing the interface. The remaining calcium ions stabilize the contacts within the coat protein dimer. The stability of the φCb5 particles decreases when calcium ions are chelated with EDTA. In contrast to other leviviruses, φCb5 particles are destabilized in solutions with elevated salt concentrations. The model of the φCb5 capsid provides an explanation of the salt-induced destabilization of φCb5 since hydrogen bonds, salt bridges and calcium ions have important role in the intersubunit interactions. Electron density of three putative RNA nucleotides per icosahedral asymmetric unit has been observed in the φCb5 structure. The nucleotides mediate contacts between the two subunits forming a dimer and a third subunit in another dimer. We suggest a model for φCb5 capsid assembly in which addition of coat protein dimers to the forming capsid is facilitated by interaction with the RNA genome. The φCb5 structure is the first example in the levivirus family that provides insight into the mechanism by which the genome - coat protein interaction may accelerate the capsid assembly and increase capsid stability.
Place, publisher, year, edition, pages
2009. Vol. 391, no 3, 635-647 p.
Virus, Structure, Assembly, Calcium, RNA
IdentifiersURN: urn:nbn:se:uu:diva-100299DOI: 10.1016/j.jmb.2009.06.047ISI: 000269097000011OAI: oai:DiVA.org:uu-100299DiVA: diva2:210076