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Science. 2012 Nov 30;338(6111):1214-7. doi: 10.1126/science.1228984. Epub 2012 Nov 8.

Cytoplasmic ATP hydrolysis powers transport of lipopolysaccharide across the periplasm in E. coli.

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Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA.


Millions of molecules of lipopolysaccharide (LPS) must be assembled on the Escherichia coli cell surface each time the cell divides. The 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 adenosine triphosphate (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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