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

2010; Nature Portfolio; Volume: 17; Issue: 6 Linguagem: Inglês

10.1038/nsmb.1836

1545-9993

Peera Jaru-Ampornpan, Kuang Shen, Quang Vinh Lam, M. Yusuf Ali, Sebastian Doniach, Tony Z. Jia, Shu‐ou Shan,

Photosynthetic Processes and Mechanisms

Membrane proteins require chaperones to keep them soluble and translocation-competent. New studies have identified a chloroplast signal recognition particle, cpSRP43, as a highly specific, ATP-independent chaperone that efficiently reverses aggregation of its substrate proteins by specific binding interactions between the chaperone and its substrate. 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.