Dynamic Association of BAM Complex Modules Includes Surface Exposure of the Lipoprotein BamC

JOURNAL OF MOLECULAR BIOLOGY

卷:422

Article

Webb, Chaille T.¹  Selkrig, Joel¹  Perry, Andrew J.¹  Noinaj, Nicholas²  Buchanan, Susan K.²  Lithgow, Trevor¹ 

[1] Monash Univ, Dept Biochem & Mol Biol, Melbourne, Vic 3800, Australia

[2] NIDDKD, Mol Biol Lab, NIH, Bethesda, MD 20892 USA

关键词: beta-barrel proteins;    Omp85;    outer membrane biogenesis;    protein transport;   

DOI  :  10.1016/j.jmb.2012.05.035

来源: Elsevier

【 摘 要 】

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.

【 授权许可】

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