A Supercomplex Spanning the Inner and Outer Membranes Mediates the Biogenesis of β-Barrel Outer Membrane Proteins in Bacteria.
β-barrel outer membrane proteins (OMPs) are ubiquitously present in Gram-negative bacteria, mitochondria and chloroplasts, and function in a variety of biological processes. The mechanism by which the hydrophobic nascent β-barrel OMPs are transported through the hydrophilic periplasmic space in bacterial cells remains elusive. Here, mainly via unnatural amino acid-mediated in vivo photo-crosslinking studies, we revealed that the primary periplasmic chaperone SurA interacts with nascent β-barrel OMPs largely via its N-domain but with β-barrel assembly machine protein BamA mainly via its satellite P2 domain, and that the nascent β-barrel OMPs interact with SurA via their N- and C-terminal regions. Additionally, via dual in vivo photo-crosslinking, we demonstrated the formation of a ternary complex involving β-barrel OMP, SurA, and BamA in cells. More importantly, we found that a supercomplex spanning the inner and outer membranes and involving the BamA, BamB, SurA, PpiD, SecY, SecE, and SecA proteins appears to exist in living cells, as revealed by a combined analyses of sucrose-gradient ultra-centrifugation, Blue native PAGE and mass spectrometry. We propose that this supercomplex integrates the translocation, transportation, and membrane insertion events for β-barrel OMP biogenesis.
From the State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences.
Yan
Y
Wang
From the State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences.
Rui
R
Wang
From the State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China.
Feng
F
Jin
From the State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences.
Yang
Y
Liu
From the State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences.
Jiayu
J
Yu
From the State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Center for Protein Science, and fuxinmiao@pku.edu.cn.
Xinmiao
X
Fu
From the State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Center for Protein Science, and changzy@pku.edu.cn.
Zengyi
Z
Chang
D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D001425:Bacterial Outer Membrane Proteins; D029968:Escherichia coli Proteins; D046912:Multiprotein Complexes
BamA; SurA; chaperone; complex; membrane biogenesis; membrane protein; protein folding; the Sec translocon; β-barrel outer membrane protein biogenesis