ExbB acts as a chaperone-like protein to stabilize TonB in the cytoplasm.
The TonB protein is required to transduce energy from the cytoplasmic membrane to outer membrane transport proteins of Gram-negative bacteria. Two accessory proteins, ExbB and ExbD, are required for TonB function and it has been suggested that TonB and ExbBD form a complex in the membrane. In this paper we demonstrate that there are two spatially distinct, functional interactions between ExbBD and TonB. First, there is an interaction between ExbBD and the N-terminal signal-like peptide of TonB, probably the formation of a stable complex in the membrane. Second, ExbB interacts with TonB in the cytoplasm. This interaction involves the domain of TonB that is normally periplasmic. Thus, this is a transient interaction which occurs during the synthesis and/or localization of TonB, implying a chaperone-like role for ExbB. The transmembrane topology of ExbB was shown to be consistent with this role.
Karlsson
M
M
Imperial Cancer Research Fund Laboratories, University of Oxford, John Radcliffe Hospital, UK.
Hannavy
K
K
Higgins
C F
CF
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000378:metabolism*; D001692:Biological Transport; D018833:Chaperonins; D003593:Cytoplasm / Q000378:metabolism*; D004734:Energy Metabolism; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins; D008565:Membrane Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011499:Protein Processing, Post-Translational; D011506:Proteins / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C052874:ExbB protein, E coli; D008565:Membrane Proteins; D011506:Proteins; D011993:Recombinant Fusion Proteins; C057616:tonB protein, Bacteria; C489181:tonB protein, E coli; C060790:exbD protein, E coli; D018833:Chaperonins