Lateral opening in the intact β-barrel assembly machinery captured by cryo-EM.
The β-barrel assembly machinery (BAM) is a ∼203 kDa complex of five proteins (BamA-E), which is essential for viability in E. coli. BAM promotes the folding and insertion of β-barrel proteins into the outer membrane via a poorly understood mechanism. Several current models suggest that BAM functions through a 'lateral gating' motion of the β-barrel of BamA. Here we present a cryo-EM structure of the BamABCDE complex, at 4.9 Å resolution. The structure is in a laterally open conformation showing that gating is independent of BamB binding. We describe conformational changes throughout the complex and interactions between BamA, B, D and E, and the detergent micelle that suggest communication between BAM and the lipid bilayer. Finally, using an enhanced reconstitution protocol and functional assays, we show that for the outer membrane protein OmpT, efficient folding in vitro requires lateral gating in BAM.
Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, University of Leeds, Mount Preston Street, Leeds LS2 9JT, UK.
Matthew G
MG
Iadanza
Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, University of Leeds, Mount Preston Street, Leeds LS2 9JT, UK.
Anna J
AJ
Higgins
Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, University of Leeds, Mount Preston Street, Leeds LS2 9JT, UK.
Bob
B
Schiffrin
Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, University of Leeds, Mount Preston Street, Leeds LS2 9JT, UK.
Antonio N
AN
Calabrese
Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, University of Leeds, Mount Preston Street, Leeds LS2 9JT, UK.
David J
DJ
Brockwell
Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, University of Leeds, Mount Preston Street, Leeds LS2 9JT, UK.
Alison E
AE
Ashcroft
Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, University of Leeds, Mount Preston Street, Leeds LS2 9JT, UK.
Sheena E
http://orcid.org/0000-0002-3079-8039
SE
Radford
Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, University of Leeds, Mount Preston Street, Leeds LS2 9JT, UK.
Neil A
NA
Ranson
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