Co-translational insertion and topogenesis of bacterial membrane proteins monitored in real time.

ABSTRACT: Integral membrane proteins insert into the bacterial inner membrane co-translationally via the translocon. Transmembrane (TM) segments of nascent proteins adopt their native topological arrangement with the N-terminus of the first TM (TM1) oriented to the outside (type I) or the inside (type II) of the cell. Here, we study TM1 topogenesis during ongoing translation in a bacterial in vitro system, applying real-time FRET and protease protection assays. We find that TM1 of the type I protein LepB reaches the translocon immediately upon emerging from the ribosome. In contrast, the type II protein EmrD requires a longer nascent chain before TM1 reaches the translocon and adopts its topology by looping inside the ribosomal peptide exit tunnel. Looping presumably is mediated by interactions betw

SUBMITTER: Mercier E 

PROVIDER: S-EPMC7396858 | biostudies-literature | 2020 Aug

REPOSITORIES: biostudies-literature