期刊
JOURNAL OF MOLECULAR BIOLOGY
卷 380, 期 3, 页码 465-475出版社
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jmb.2008.04.065
关键词
mass spectrometry; cryo-electron microscopy; bacteriophage; assembly; scaffolding protein
资金
- NIAID NIH HHS [AI067654, R21 AI067654-02, R21 AI071982-01, R21 AI067654, R21 AI071982, AI071982] Funding Source: Medline
The Staphylococcus aureus pathogenicity island SaPI1 carries the gene for the toxic shock syndrome toxin (TSST-1) and can be mobilized by infection with S. aureus helper phage 80 alpha. SaPI1 depends on the helper phage for excision, replication and genome packaging. The SaPI1-transducing particles comprise proteins encoded by the helper phage, but have a smaller capsid commensurate with the smaller size of the SaPI1 genome. Previous studies identified only 80 alpha-encoded proteins in mature SaPI1 virions, implying that the presumptive SaPI1 capsid size determination function(s) must act transiently during capsid assembly or maturation. In this study, 80 alpha and SaPI1 procapsids were produced by induction of phage mutants lacking functional 80 alpha or SaPI1 small terminase subunits. By cryo-electron microscopy, these procapsids were found to have a round shape and an internal scaffolding core. Mass spectrometry was used to identify all 80 alpha-encoded structural proteins in 80 alpha and SaPI1 procapsids, including several that had not previously been found in the mature capsids. In addition, SaPI1 procapsids contained at least one SaPI1-encoded protein that has been implicated genetically in capsid size determination. Mass spectrometry on full-length phage proteins showed that the major capsid protein and the scaffolding protein are N-terminally processed in both 80 alpha and SaPI1 procapsids. (C) 2008 Elsevier Ltd. All rights reserved.
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