Microbiology

Lipoprotein ABCs

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Science  31 Mar 2000:
Vol. 287, Issue 5462, pp. 2377
DOI: 10.1126/science.287.5462.2377g

The ATP-binding cassette (ABC) proteins are a family of membrane transporters responsible for pumping drugs and other molecules across cellular membranes. Yakushi et al. have discovered and functionally reconstituted in proteoliposomes an ABC protein that acts in a radically different fashion—to promote the release of lipoproteins from bacterial membranes during lipoprotein transfer from the inner to the outer membrane of gram negative bacteria. The new ABC protein complex, LolCDE, is found in the Escherichia coli inner membrane. After translocation across the inner membrane, lipoproteins (Out) bind to LolCDE and then are transferred to the periplasmic chaperone LolA in a step that requires ATP hydrolysis. Next, LolA carries this cargo to the lipoprotein receptor LolB, and the journey ends with incorporation of the lipoprotein into the outer membrane. This specialized machinery may be particularly important in gram negative bacteria due to the large number of outer membrane lipoproteins, which do not contain any of the classical membrane targeting or anchoring signals.—SMH

Nature Cell Biol.2, 212 (2000).

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