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Nat Struct Mol Biol. 2005 Dec;12(12):1116-22. Epub 2005 Nov 20.

RNA-mediated interaction between the peptide-binding and GTPase domains of the signal recognition particle.

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Department of Molecular and Cell Biology, University of California, Berkeley, California 94705, USA.


The signal recognition particle (SRP) targets nascent proteins to cellular membranes for insertion or secretion by recognizing polypeptides containing an N-terminal signal sequence as they emerge from the ribosome. GTP-dependent binding of SRP to its receptor protein leads to controlled release of the nascent chain into a membrane-spanning translocon pore. Here we show that the association of the SRP with its receptor triggers a marked conformational change in the complex, localizing the SRP RNA and the adjacent signal peptide-binding site at the SRP-receptor heterodimer interface. The orientation of the RNA suggests how peptide binding and GTP hydrolysis can be coupled through direct structural contact during cycles of SRP-directed protein translocation.

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