Competing scaffolding proteins determine capsid size during mobilization of Staphylococcus aureus pathogenicity islands
- National Institutes of Health, United States
- Virginia Commonwealth University, United States
- University of Alabama at Birmingham, United States
- Direct Electron, LP, United States
- Florida State University, United States
Abstract
Staphylococcus aureus pathogenicity islands (SaPIs), such as SaPI1, exploit specific helper bacteriophages, like 80a, for their high frequency mobilization, a process termed 'molecular piracy'. SaPI1 redirects the helper's assembly pathway to form small capsids that can only accommodate the smaller SaPI1 genome, but not a complete phage genome. SaPI1 encodes two proteins, CpmA and CpmB, that are responsible for this size redirection. We have determined the structures of the 80a and SaPI1 procapsids to near-atomic resolution by cryo-electron microscopy, and show that CpmB competes with the 80a scaffolding protein (SP) for a binding site on the capsid protein (CP), and works by altering the angle between capsomers. We probed these interactions genetically and identified second-site suppressors of lethal mutations in SP. Our structures show, for the first time, the detailed interactions between SP and CP in a bacteriophage, providing unique insights into macromolecular assembly processes.
Data availability
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Capsid protein and C-terminal part of scaffolding protein in the Staphylococcus aureus phage 80alpha procapsidPublicly available at the EMBL-EBI EM Data Bank with accession number -EMDB-7030.
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Capsid protein and C-terminal part of scaffolding protein in the Staphylococcus aureus phage 80alpha procapsidPublicly available at the RCSB Protein Data Bank with accession number 6B0X.
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Capsid protein and C-terminal part of CpmB protein in the Staphylococcus aureus pathogenicity island 1 80alpha-derived procapsidPublicly available at the EMBL-EBI EM Data Bank with accession number -EMDB-7035.
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Capsid protein and C-terminal part of CpmB protein in the Staphylococcus aureus pathogenicity island 1 80alpha-derived procapsidPublicly available at the RCSB Protein Data Bank with accession number 6B23.
Article and author information
Author details
Funding
National Institutes of Health (R01 AI083255)
- Terje Dokland
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2017, Dearborn et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Competing scaffolding proteins determine capsid size during mobilization of Staphylococcus aureus pathogenicity islands
eLife 6:e30822.
https://doi.org/10.7554/eLife.30822
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