title: SRP RNA controls a conformational switch regulating the SRP-SRP receptor interaction.
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.
authors.affiliation: Howard Hughes Medical Institute, University of California at San Francisco, 600 16th Street, San Francisco, California 94158, USA.
authors.forename: Saskia B
authors.initials: SB
authors.lastname: Neher
authors.forename: Niels
authors.initials: N
authors.lastname: Bradshaw
authors.forename: Stephen N
authors.initials: SN
authors.lastname: Floor
authors.forename: John D
authors.initials: JD
authors.lastname: Gross
authors.forename: Peter
authors.initials: P
authors.lastname: Walter
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006868:Hydrolysis; D046911:Macromolecular Substances / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D012329:RNA, Bacterial / Q000737:chemistry* / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D018000:Receptors, Peptide / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018271:Signal Recognition Particle / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: C409968:4.5S RNA; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C082931:Ffh protein, E coli; C087406:FtsY protein, Bacteria; D046911:Macromolecular Substances; D012329:RNA, Bacterial; D018160:Receptors, Cytoplasmic and Nuclear; D018000:Receptors, Peptide; D011994:Recombinant Proteins; D018271:Signal Recognition Particle; C036318:signal peptide receptor; D006160:Guanosine Triphosphate