The roles of SaPI1 proteins gp7 (CpmA) and gp6 (CpmB) in capsid size determination and helper phage interference

Abstract SaPIs are molecular pirates that exploit helper bacteriophages for their own high frequency mobilization. One striking feature of helper exploitation by SaPIs is redirection of the phage capsid assembly pathway to produce smaller phage-like particles with T =4 icosahedral symmetry rather th...

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Bibliographic Details
Published in:Virology (New York, N.Y.) N.Y.), 2012-10, Vol.432 (2), p.277-282
Main Authors: Damle, Priyadarshan K, Wall, Erin A, Spilman, Michael S, Dearborn, Altaira D, Ram, Geeta, Novick, Richard P, Dokland, Terje, Christie, Gail E
Format: Article
Language:English
Subjects:
Bacteriophage assembly
Capsid - metabolism
Capsid - ultrastructure
Capsid Proteins - genetics
Capsid Proteins - metabolism
Cryo-electron microscopy
Cryoelectron Microscopy
Genomic Islands - genetics
Helper Viruses - chemistry
Helper Viruses - genetics
Infectious Disease
Molecular piracy
Procapsid
Staphylococcus aureus - genetics
Staphylococcus aureus - pathogenicity
Staphylococcus aureus - virology
Staphylococcus aureus pathogenicity island
Staphylococcus Phages - chemistry
Staphylococcus Phages - genetics
Staphylococcus Phages - metabolism
Virus Assembly
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Summary:Abstract SaPIs are molecular pirates that exploit helper bacteriophages for their own high frequency mobilization. One striking feature of helper exploitation by SaPIs is redirection of the phage capsid assembly pathway to produce smaller phage-like particles with T =4 icosahedral symmetry rather than T =7 bacteriophage capsids. Small capsids can accommodate the SaPI genome but not that of the helper phage, leading to interference with helper propagation. Previous studies identified two proteins encoded by the prototype element SaPI1, gp6 and gp7, in SaPI1 procapsids but not in mature SaPI1 particles. Dimers of gp6 form an internal scaffold, aiding fidelity of small capsid assembly. Here we show that both SaPI1 gp6 (CpmB) and gp7 (CpmA) are necessary and sufficient to direct small capsid formation. Surprisingly, failure to form small capsids did not restore wild-type levels of helper phage growth, suggesting an additional role for these SaPI1 proteins in phage interference.
ISSN:0042-6822
1096-0341
DOI:10.1016/j.virol.2012.05.026