Article abstract
Nature Structural & Molecular Biology 15, 916 - 923 (2008)
Published online: 10 August 2008 | doi:10.1038/nsmb.1467
SRP RNA controls a conformational switch regulating the SRP–SRP receptor interaction
Saskia B Neher1,2,5, Niels Bradshaw1,2,5, Stephen N Floor3,4, John D Gross3 & Peter Walter1,2
Abstract
The interaction of the signal-recognition particle (SRP) with its receptor (SR) mediates co-translational protein targeting to the membrane. SRP and SR interact via their homologous core GTPase domains and N-terminal four-helix bundles (N domains). SRP–SR complex formation is slow unless catalyzed by SRP's essential RNA component. We show that truncation of the first helix of the N domain (helix N1) of both proteins dramatically accelerates their interaction. SRP and SR with helix N1 truncations interact at nearly the RNA-catalyzed rate in the absence of RNA. NMR spectroscopy and analysis of GTPase activity show that helix N1 truncation in SR mimics the conformational switch caused by complex formation. These results demonstrate that the N-terminal helices of SRP and SR are autoinhibitory for complex formation in the absence of SRP RNA, suggesting a mechanism for RNA-mediated coordination of the SRP–SR interaction.
- Howard Hughes Medical Institute, University of California at San Francisco, 600 16th Street, San Francisco, California 94158, USA
- Department of Biochemistry and Biophysics, University of California at San Francisco, 600 16th Street, San Francisco, California 94158, USA
- Department of Pharmaceutical Chemistry, University of California at San Francisco, 600 16th Street, San Francisco, California 94158, USA
- Graduate Group in Biophysics, University of California at San Francisco, 600 16th Street, San Francisco, California 94158, USA
- These authors contributed equally to this work.
Correspondence to: Peter Walter1,2 e-mail: pwalter@biochem.ucsf.edu
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