Defining the roles of the periplasmic chaperones SurA, Skp, and DegP in Escherichia coli.
Integral beta-barrel proteins (OMPs) are a major class of outer membrane proteins in Gram-negative bacteria. In Escherichia coli, these proteins are synthesized in the cytoplasm, translocated across the inner membrane via the Sec machinery, and assembled in the outer membrane through an unknown mechanism that requires the outer membrane YaeT complex and the periplasmic chaperones SurA, DegP, and Skp. Here, we have established the relationship between these three chaperones providing insight into the mechanism of OMP biogenesis using depletion analysis. Depletion of SurA alone results in a marked decrease in outer membrane density, while the loss of DegP and Skp has no effect on outer membrane composition. Furthermore, we demonstrate that SurA and YaeT interact directly in vivo. Based on these results, we suggest that SurA is the primary chaperone responsible for the periplasmic transit of the bulk mass of OMPs to the YaeT complex. The role of Skp and DegP is amplified in the absence of SurA. Evidence presented suggests that DegP/Skp function to rescue OMPs that fall off the SurA pathway. The seemingly redundant periplasmic chaperones do function in parallel, but the relative importance of the primary function of each pathway depends on whether or not cells are under stress.
Sklar
Joseph G
JG
Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA.
Wu
Tao
T
Kahne
Daniel
D
Silhavy
Thomas J
TJ
D001425:Bacterial Outer Membrane Proteins / Q000032:analysis / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D006360:Heat-Shock Proteins / Q000235:genetics / Q000502:physiology*; D018832:Molecular Chaperones / Q000235:genetics / Q000502:physiology*; D019696:Peptidylprolyl Isomerase / Q000235:genetics / Q000502:physiology*; D033903:Periplasmic Proteins / Q000235:genetics / Q000502:physiology*; D018272:Porins / Q000032:analysis / Q000378:metabolism; D017510:Protein Folding; D011991:Receptors, Virus / Q000032:analysis / Q000378:metabolism; D012697:Serine Endopeptidases / Q000235:genetics / Q000502:physiology*
D001425:Bacterial Outer Membrane Proteins; C503914:BamA protein, E coli; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D033903:Periplasmic Proteins; D018272:Porins; D011991:Receptors, Virus; C016532:maltoporins; C072721:Skp protein, E coli; C078167:OMPA outer membrane proteins; C061682:DegP protease; D012697:Serine Endopeptidases; C490900:SurA protein, E coli; D019696:Peptidylprolyl Isomerase