Cytoplasmic ATP Hydrolysis Powers Transport of Lipopolysaccharide Across the Periplasm in E. coli

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Science  08 Nov 2012:
DOI: 10.1126/science.1228984

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Millions of molecules of lipopolysaccharide (LPS) must be assembled on the E. coli cell surface every division. Biogenesis of LPS requires seven essential lipopolysaccharide transport (Lpt) proteins to move LPS from the inner membrane through the periplasm to the cell surface. However, no intermediate transport states have been observed. We developed methods to observe intermediate LPS molecules bound to Lpt proteins in the process of being transported in vivo. Movement of individual LPS molecules along these binding sites required multiple rounds of ATP hydrolysis in vitro, which suggests that ATP is used to push a continuous stream of LPS through a transenvelope bridge in discrete steps against a concentration gradient.

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