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

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 119; no. 35; p. e2205810119
• Main Authors: Mermans, Daphne, Nicolaus, Felix, Fleisch, Klara, von Heijne, Gunnar
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 30.08.2022
• Subjects: amino terminal sequence; antiporter; Antiporters; Antiporters - metabolism; Biological Sciences; carboxy terminal sequence; Chains; cotranslational dimerization; cotranslational folding; dimerization; E coli; EmrE; EmrE protein; Escherichia coli; Escherichia coli - genetics; Escherichia coli - metabolism; Escherichia coli protein; Escherichia coli Proteins; Escherichia coli Proteins - metabolism; genetics; Insertion; membrane protein; membrane protein biogenesis; Membrane Proteins; Membranes; metabolism; monomer; Monomers; nonhuman; peptide; Peptides; Peptides - metabolism; polyacrylamide gel electrophoresis; polypeptide; Polypeptides; protein assembly; Protein Biosynthesis; protein engineering; Protein Folding; protein interaction; protein structure; protein synthesis; Proteins; ribosome; unclassified drug; cotranslational dimerization; membrane protein biogenesis; EmrE; cotranslational folding
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.2205810119

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 also possible for integral membrane proteins is, however, unknown. 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 inner membrane protein EmrE. Similar cotranslational interactions are also seen when the two monomers are fused into a single polypeptide. Further, we uncover an apparent intrachain interaction between E in transmembrane helix 1 (TMH1) and S in TMH3 that forms at a precise nascent chain length during cotranslational membrane insertion of an EmrE monomer. Like soluble proteins, inner membrane proteins thus appear to be able to both start to fold and start to dimerize during the cotranslational membrane insertion process.