Biochemistry

A Nanomembrane

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Science  13 Apr 2007:
Vol. 316, Issue 5822, pp. 174
DOI: 10.1126/science.316.5822.174c

The technical difficulties of working with membrane proteins, which sport extensive hydrophobic and hydrophilic surfaces (not to mention a heterogeneous collection of attached sugars), are matched only by the ease with which cells manage to handle them. In bacteria, the trimeric complex SecYEG accepts substrate proteins made in the cytoplasm and either passes them through the inner membrane to the periplasmic space or ejects them laterally straight into the inner membrane itself (how outer membrane proteins are dealt with is a whole other story). Some of the substrates are delivered by the cytosolic motor protein SecA, but the amphiphilic character of the protein translocation machinery has made it hard to probe the structural state of functional SecA-SecYEG interactions. Alami et al. have reconstituted SecYEG monomers into a membrane-like lipid/protein construct, referred to as a nanodisc; adding dimeric SecA to these nanodiscs results in dissociation of the dimers and binding of monomeric SecA to SecYEG and the consequent stimulation of SecA ATPase activity. — GJC

EMBO J. 26, 10.1038/sj.emboj.7601661 (2007).

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