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Nat Struct Mol Biol. 2010 Jun;17(6):696-702. doi: 10.1038/nsmb.1836. Epub 2010 Apr 27.

ATP-independent reversal of a membrane protein aggregate by a chloroplast SRP subunit.

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Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California, USA.


Membrane proteins impose enormous challenges to cellular protein homeostasis during their post-translational targeting, and they require chaperones to keep them soluble and translocation competent. Here we show that a novel targeting factor in the chloroplast signal recognition particle (cpSRP), cpSRP43, is a highly specific molecular chaperone that efficiently reverses the aggregation of its substrate proteins. In contrast to 'ATPases associated with various cellular activities' (AAA(+)) chaperones, cpSRP43 uses specific binding interactions with its substrate to mediate its 'disaggregase' activity. This disaggregase capability can allow targeting machineries to more effectively capture their protein substrates and emphasizes a close connection between protein folding and trafficking processes. Moreover, cpSRP43 provides the first example to our knowledge of an ATP-independent disaggregase and shows that efficient reversal of protein aggregation can be attained by specific binding interactions between a chaperone and its substrate.

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