期刊
JOURNAL OF MOLECULAR BIOLOGY
卷 422, 期 4, 页码 545-555出版社
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jmb.2012.05.035
关键词
beta-barrel proteins; Omp85; outer membrane biogenesis; protein transport
资金
- National Health and Medical Research Council (NHMRC) of Australia through an NHMRC [606788]
- NHMRC Postgraduate Research Scholarship
- Intramural Research Program of the National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases
The beta-barrel assembly machinery (BAM) complex drives the assembly of beta-barrel proteins into the outer membrane of gram-negative bacteria. It is composed of five subunits: BamA, BamB, BamC, BamD, and BamE. We find that the BAM complex isolated from the outer membrane of Escherichia coli consists of a core complex of BamA:B:C:D:E and, in addition, a BamA:B module and a BamC:D module. In the absence of BamC, these modules are destabilized, resulting in increased protease susceptibility of BamD and BamB. While the N-terminus of BamC carries a highly conserved region crucial for stable interaction with BamD, immunofluorescence, immunoprecipitation, and protease-sensitivity assays show that the C-terminal domain of BamC, composed of two helix-grip motifs, is exposed on the surface of E. coli. This unexpected topology of a bacterial lipoprotein is reminiscent of the analogous protein subunits from the mitochondrial beta-barrel insertion machinery, the SAM complex. The modular arrangement and topological features provide new insight into the architecture of the BAM complex, towards a better understanding of the mechanism driving beta-barrel membrane protein assembly. (C) 2012 Elsevier Ltd. All rights reserved.
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