YidC Protein, a Molecular Chaperone for LacY Protein Folding via the SecYEG Protein Machinery

• Published in: The Journal of biological chemistry 2013-09, Vol.288 (39), p.28180-28194
• Main Authors: Zhu, Lu, Kaback, H. Ronald, Dalbey, Ross E.
• Format: Article
• Language: English
• Subjects: Chaperone; Chaperonin; Disulfides - chemistry; Escherichia coli - enzymology; Escherichia coli Proteins - metabolism; LacY; Membrane Biogenesis; Membrane Biology; Membrane Enzymes; Membrane Insertion; Membrane Proteins; Membrane Proteins - metabolism; Membrane Transport Proteins - metabolism; Models, Molecular; Molecular Chaperones - metabolism; Monosaccharide Transport Proteins - metabolism; Mutagenesis, Site-Directed; Mutation; Peptide Hydrolases - chemistry; Protein Binding; Protein Folding; Protein Structure, Tertiary; SEC Translocation Channels; Symporters - metabolism; YidC
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M113.491613

To understand how YidC and SecYEG function together in membrane protein topogenesis, insertion and folding of the lactose permease of Escherichia coli (LacY), a 12-transmembrane helix protein LacY that catalyzes symport of a galactoside and an H+, was studied. Although both the SecYEG machinery and signal recognition particle are required for insertion of LacY into the membrane, YidC is not required for translocation of the six periplasmic loops in LacY. Rather, YidC acts as a chaperone, facilitating LacY folding. Upon YidC depletion, the conformation of LacY is perturbed, as judged by monoclonal antibody binding studies and by in vivo cross-linking between introduced Cys pairs. Disulfide cross-linking also demonstrates that YidC interacts with multiple transmembrane segments of LacY during membrane biogenesis. Moreover, YidC is strictly required for insertion of M13 procoat protein fused into the middle cytoplasmic loop of LacY. In contrast, the loops preceding and following the inserted procoat domain are dependent on SecYEG for insertion. These studies demonstrate close cooperation between the two complexes in membrane biogenesis and that YidC functions primarily as a foldase for LacY. Background: YidC is required for LacY folding, but the details of this process are not clear. Results: YidC binds multiple LacY TM domains and is involved in LacY folding but not insertion. Conclusion: YidC binding to LacY directs the proper helix-helix interactions of LacY. Significance: This is the first detailed in vivo analysis of LacY insertion and YidC-LacY interactions.