Cross-species chimeras reveal BamA POTRA and ?-barrel domains must be fine-tuned for efficient OMP insertion.

ABSTRACT: BAM is a conserved molecular machine, the central component of which is BamA. Orthologues of BamA are found in all Gram-negative bacteria, chloroplasts and mitochondria where it is required for the folding and insertion of ?-barrel containing integral outer membrane proteins (OMPs) into the outer membrane. BamA binds unfolded ?-barrel precursors via the five polypeptide transport-associated (POTRA) domains at its N-terminus. The C-terminus of BamA folds into a ?-barrel domain, which tethers BamA to the outer membrane and is involved in OMP insertion. BamA orthologues are found in all Gram-negative bacteria and appear to function in a species-specific manner. Here we investigate the nature of this species-specificity by examining whether chimeric Escherichia coli?BamA fusion proteins, carrying either the ?-barrel or POTRA domains from various BamA orthologues, can functionally replace E.?coli?BamA. We demonstrate that the ?-barrel domains of many BamA orthologues are functionally interchangeable. We show that defects in the orthologous POTRA domains can be rescued by compensatory mutations within the ?-barrel. These data reveal that the POTRA and barrel domains must be precisely aligned to ensure efficient OMP insertion.

SUBMITTER: Browning DF 

PROVIDER: S-EPMC4950039 | biostudies-literature | 2015 Aug

REPOSITORIES: biostudies-literature