@article{fa66ee11eb5c40d99aa30a627290fc40,
title = "Cryo-EM structures reveal multiple stages of bacterial outer membrane protein folding",
abstract = "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.",
keywords = "BAM, membrane dynamics, membrane protein folding, outer membrane protein, β barrel",
author = "Doyle, {Matthew Thomas} and Jimah, {John R.} and Tyrone Dowdy and Ohlemacher, {Shannon I.} and Mioara Larion and Hinshaw, {Jenny E.} and Bernstein, {Harris D.}",
note = "Funding Information: This work was supported by the NIDDK and NCI Intramural Research Programs . J.R.J. is a recipient of an NIGMS MOSAIC K99/R00 award. The structural studies were performed at the NIH Multi-Institute Cryo-EM Facility (MICEF) and the NIDDK cryo-EM core facility and utilized computational resources from the NIH HPC Biowulf cluster ( http://hpc.nih.gov ). We thank Huaibin Wang, Haifeng He, and Bertram Canagarajah for technical support with cryo-EM and computing. Funding Information: This work was supported by the NIDDK and NCI Intramural Research Programs. J.R.J. is a recipient of an NIGMS MOSAIC K99/R00 award. The structural studies were performed at the NIH Multi-Institute Cryo-EM Facility (MICEF) and the NIDDK cryo-EM core facility and utilized computational resources from the NIH HPC Biowulf cluster (http://hpc.nih.gov). We thank Huaibin Wang, Haifeng He, and Bertram Canagarajah for technical support with cryo-EM and computing. The study was conceived by M.T.D. and H.D.B. but all authors contributed to experimental design. The experiments, data processing, and analyses were conducted by M.T.D. and J.R.J. Lipidomic experiments and analysis were conducted by T.D. S.I.O. and M.L. The paper was written and edited by all authors. The project was supervised by J.E.H. and H.D.B. The authors declare no competing interests. Publisher Copyright: {\textcopyright} 2022",
year = "2022",
month = mar,
day = "31",
doi = "10.1016/j.cell.2022.02.016",
language = "English (US)",
volume = "185",
pages = "1143--1156.e13",
journal = "Cell",
issn = "0092-8674",
publisher = "Cell Press",
number = "7",
}