Journal
JOURNAL OF MOLECULAR BIOLOGY
Volume 383, Issue 3, Pages 603-614Publisher
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jmb.2008.08.047
Keywords
adaptor protein; chaperone; helical bundle; secretion system; virulence factor
Categories
Funding
- Biotechnology and Biological Sciences Research Council (UK)
- The Wellcome Trust [082596, 083481]
- Biotechnology and Biological Sciences Research Council [BBS/B/14434] Funding Source: researchfish
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Staphylococcus aureus pathogenesis depends on a specialized protein secretion system (ESX-1) that delivers a range of virulence factors to assist infectivity. We report the characterization of two such factors, EsxA and EsxB, small acidic dimeric proteins carrying a distinctive WXG motif. EsxA crystallized in triclinic and monoclinic forms and high-resolution structures were determined. The asymmetric unit of each crystal form is a dimer. The EsxA subunit forms an elongated cylindrical structure created from side-by-side alpha-helices linked with a hairpin bend formed by the WXG motif. Approximately 25% of the solvent accessible surface area of each subunit is involved in interactions, predominantly hydrophobic, with the partner subunit. Secondary-structure predictions suggest that EsxB displays a similar structure. The WXG motif helps to create a shallow cleft at each end of the dimer, forming a short beta-sheet-like feature with an N-terminal segment of the partner subunit. Structural and sequence comparisons, exploiting biological data on related proteins found in Mycobacterium tuberculosis, suggest that this fan-Lily of proteins may contribute to pathogenesis by transporting protein cargo through the ESX-1 system exploiting a C-terminal secretion signal and/or are capable of acting as adaptor proteins to facilitate interactions with host receptor proteins. (C) 2008 Elsevier Ltd. All rights reserved.
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