Regulated assembly of the transenvelope protein complex required for lipopolysaccharide export.
Gram-negative bacteria are impervious to many drugs and environmental stresses because they possess an outer membrane (OM) containing lipopolysaccharide (LPS). LPS is biosynthesized at the cytoplasmic (inner) membrane and is transported to the OM by an unknown mechanism involving the LPS transport proteins, LptA-G. These proteins have been proposed to form a bridge between the two membranes; however, it is not known how this bridge is assembled to prevent mistargeting of LPS. We use in vivo photo-cross-linking to reveal the specific protein-protein interaction sites that give rise to the Lpt bridge. We also show that the formation of this transenvelope bridge cannot proceed before the correct assembly of the LPS translocon in the OM. This ordered sequence of events may ensure that LPS is never transported to the OM if it cannot be translocated across it to the cell surface.
Chemical Biology Graduate Program, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, USA.
Elizaveta
E
Freinkman
Suguru
S
Okuda
Natividad
N
Ruiz
Daniel
D
Kahne
D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D004220:Disulfides / Q000737:chemistry; D004926:Escherichia coli / Q000166:cytology* / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000378:metabolism*; D008958:Models, Molecular; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid
D004220:Disulfides; D029968:Escherichia coli Proteins; D008070:Lipopolysaccharides