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A TonB‐like protein and a novel membrane protein containing an ATP‐binding cassette function together in exotoxin secretion
Author(s) -
Howard S. Peter,
Meiklejohn Heather G.,
Shivak David,
Jahagirdar Ravindra
Publication year - 1996
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.1996.d01-1713.x
Subject(s) - biology , secretion , bacterial outer membrane , transport protein , aerolysin , microbiology and biotechnology , inner membrane , secretory protein , biochemistry , membrane protein , membrane topology , vesicle associated membrane protein 8 , translocon , membrane , escherichia coli , gene , virulence
Protein secretion by many Gram‐negative bacteria occurs via the type II pathway involving translocation across the cytoplasmic and outer membranes in separate steps. The mechanism by which metabolic energy is supplied to the translocation across the outer membrane is unknown. Here we show that two Aeromonas hydrophila inner membrane proteins, ExeA and ExeB, are required for this process. ExeB bears sequence as well as topological similarity to TonB, a protein which opens gated ports for the inward translocation of ligands across the outer membrane. ExeA is a novel membrane protein which contains a consensus ATP‐binding site. Mutations in this site dramatically decreased the rate of secretion of the toxin aerolysin from the cell. ExeB was stable when overproduced in the presence of ExeA, but was degraded when synthesized in its absence, indicating that the two proteins form a complex. These results suggest that ExeA and ExeB may act together to transduce metabolic energy to the opening of a secretion port in the outer membrane.