Title | Cryo-EM structures reveal multiple stages of bacterial outer membrane protein folding. |
Publication Type | Journal Article |
Year of Publication | 2022 |
Authors | Doyle, MThomas, Jimah, JR, Dowdy, T, Ohlemacher, SI, Larion, M, Hinshaw, JE, Bernstein, HD |
Journal | Cell |
Volume | 185 |
Issue | 7 |
Pagination | 1143-1156.e13 |
Date Published | 2022 Mar 31 |
ISSN | 1097-4172 |
Keywords | Bacterial Outer Membrane Proteins, Cryoelectron Microscopy, Escherichia coli, Escherichia coli Proteins, Protein Folding |
Abstract | <p>Transmembrane β barrel proteins are folded into the outer membrane (OM) of Gram-negative bacteria by the β barrel assembly machinery (BAM) via a poorly understood process that occurs without known external energy sources. Here, we used single-particle cryo-EM to visualize the folding dynamics of a model β barrel protein (EspP) by BAM. We found that BAM binds the highly conserved "β signal" motif of EspP to correctly orient β strands in the OM during folding. We also found that the folding of EspP proceeds via "hybrid-barrel" intermediates in which membrane integrated β sheets are attached to the essential BAM subunit, BamA. The structures show an unprecedented deflection of the membrane surrounding the EspP intermediates and suggest that β sheets progressively fold toward BamA to form a β barrel. Along with in vivo experiments that tracked β barrel folding while the OM tension was modified, our results support a model in which BAM harnesses OM elasticity to accelerate β barrel folding.</p> |
DOI | 10.1016/j.cell.2022.02.016 |
Alternate Journal | Cell |
PubMed ID | 35294859 |
PubMed Central ID | PMC8985213 |
Grant List | K99 GM140220 / GM / NIGMS NIH HHS / United States R00 GM140220 / GM / NIGMS NIH HHS / United States ZIA DK052037 / ImNIH / Intramural NIH HHS / United States |