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Proc Natl Acad Sci U S A. 2016 Aug 2;113(31):8717-22. doi: 10.1073/pnas.1604100113. Epub 2016 Jul 20.

Characterization of a stalled complex on the β-barrel assembly machine.

Author information

1
Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138; Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138;
2
Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138;
3
Department of Molecular Biology, Princeton University, Princeton, NJ, 08544;
4
Department of Microbiology, The Ohio State University, Columbus, OH 43210;
5
Department of Microbiology, The Ohio State University, Columbus, OH 43210; ruiz.82@osu.edu tsilhavy@princeton.edu kahne@chemistry.harvard.edu.
6
Department of Molecular Biology, Princeton University, Princeton, NJ, 08544; ruiz.82@osu.edu tsilhavy@princeton.edu kahne@chemistry.harvard.edu.
7
Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138; Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115 ruiz.82@osu.edu tsilhavy@princeton.edu kahne@chemistry.harvard.edu.

Abstract

The assembly of β-barrel proteins into membranes is mediated by an evolutionarily conserved machine. This process is poorly understood because no stable partially folded barrel substrates have been characterized. Here, we slowed the folding of the Escherichia coli β-barrel protein, LptD, with its lipoprotein plug, LptE. We identified a late-stage intermediate in which LptD is folded around LptE, and both components interact with the two essential β-barrel assembly machine (Bam) components, BamA and BamD. We propose a model in which BamA and BamD act in concert to catalyze folding, with the final step in the process involving closure of the ends of the barrel with release from the Bam components. Because BamD and LptE are both soluble proteins, the simplest model consistent with these findings is that barrel folding by the Bam complex begins in the periplasm at the membrane interface.

KEYWORDS:

Bam complex; outer membrane; protein folding; β-barrel

PMID:
27439868
PMCID:
PMC4978274
DOI:
10.1073/pnas.1604100113
[Indexed for MEDLINE]
Free PMC Article

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