Formation of a β-barrel membrane protein is catalyzed by the interior surface of the assembly machine protein BamA
- Harvard University, United States
Abstract
The β-barrel assembly machine (Bam) complex in Gram-negative bacteria and its counterparts in mitochondria and chloroplasts fold and insert outer membrane β-barrel proteins. BamA, an essential component of the complex, is itself a β-barrel and is proposed to play a central role in assembling other barrel substrates. Here, we map the path of substrate insertion by the Bam complex using site-specific crosslinking to understand the molecular mechanisms that control β-barrel folding and release. We find that the C-terminal strand of the substrate is stably held by BamA and that the N-terminal strands of the substrate are assembled inside the BamA β-barrel. Importantly, we identify contacts between the assembling β-sheet and the BamA interior surface that determine the rate of substrate folding. Our results support a model in which the interior wall of BamA acts as a chaperone to catalyze β-barrel assembly.
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All data generated or analyzed during this study are included in the manuscript and supporting files.
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Funding
National Institute of Allergy and Infectious Diseases (AI081059)
- James Lee
- David Tomasek
- Thiago Santos
- Mary D May
- Ina Meuskens
- Daniel Kahne
National Institute of General Medical Sciences (F31GM116210)
- James Lee
National Institute of Allergy and Infectious Diseases (T32AI132120)
- Mary D May
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2019, Lee 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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Formation of a β-barrel membrane protein is catalyzed by the interior surface of the assembly machine protein BamA
eLife 8:e49787.
https://doi.org/10.7554/eLife.49787
