Lateral Opening in the Intact β-barrel Assembly Machinery Captured by Cryo-EM

Overview

Journal Nat Commun

Specialty Biology

Date 2016 Oct 1

PMID 27686148

Citations 106

Authors

Matthew G Iadanza

Anna J Higgins

Bob Schiffrin

Antonio N Calabrese

David J Brockwell

Alison E Ashcroft

Sheena E Radford

Neil A Ranson

Affiliations

Soon will be listed here.

Abstract

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.

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