Cotranslational folding and assembly of the dimeric E. coli inner membrane protein EmrE

Abstract

In recent years, it has become clear that many homo- and heterodimeric cytoplasmic proteins in both prokaryotic and eukaryotic cells start to dimerize cotranslationally, i.e., while at least one of the two chains is still attached to the ribosome. Whether this is possible also for integral membrane proteins is unknown, however. Here, we apply Force Profile Analysis (FPA) – a method where a translational arrest peptide (AP) engineered into the polypeptide chain is used to detect force generated on the nascent chain during membrane insertion – to demonstrate cotranslational interactions between a fully membrane-inserted monomer and a nascent, ribosome-tethered monomer of the E. coli inner membrane protein EmrE.