C-terminal kink formation is required for lateral gating in BamA.

ABSTRACT: In Gram-negative bacteria, the outer membrane contains primarily ?-barrel transmembrane proteins and lipoproteins. The insertion and assembly of ?-barrel outer-membrane proteins (OMPs) is mediated by the ?-barrel assembly machinery (BAM) complex, the core component of which is the 16-stranded transmembrane ?-barrel BamA. Recent studies have indicated a possible role played by the seam between the first and last ?-barrel strands of BamA in the OMP insertion process through lateral gating and a destabilized membrane region. In this study, we have determined the stability and dynamics of the lateral gate through over 12.5 ?s of equilibrium simulations and 4 ?s of free-energy calculations. From the equilibrium simulations, we have identified a persistent kink in the C-terminal strand and observed spontaneous lateral-gate separation in a mimic of the native bacterial outer membrane. Free-energy calculations of lateral gate opening revealed a significantly lower barrier to opening in the C-terminal kinked conformation; mutagenesis experiments confirm the relevance of C-terminal kinking to BamA structure and function.

SUBMITTER: Lundquist K 

PROVIDER: S-EPMC6112699 | biostudies-literature | 2018 Aug

REPOSITORIES: biostudies-literature