Formation of a ?-barrel membrane protein is catalyzed by the interior surface of the assembly machine protein BamA.

ABSTRACT: The ?-barrel assembly machine (Bam) complex in Gram-negative bacteria and its counterparts in mitochondria and chloroplasts fold and insert outer membrane ?-barrel proteins. BamA, an essential component of the complex, is itself a ?-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 ?-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 ?-barrel. Importantly, we identify contacts between the assembling ?-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 ?-barrel assembly.

SUBMITTER: Lee J 

PROVIDER: S-EPMC6887485 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature