title: The structural basis of FtsY recruitment and GTPase activation by SRP RNA.
abstract: The universally conserved signal recognition particle (SRP) system mediates the targeting of membrane proteins to the translocon in a multistep process controlled by GTP hydrolysis. Here we present the 2.6 Å crystal structure of the GTPase domains of the E. coli SRP protein (Ffh) and its receptor (FtsY) in complex with the tetraloop and the distal region of SRP-RNA, trapped in the activated state in presence of GDP:AlF4. The structure reveals the atomic details of FtsY recruitment and, together with biochemical experiments, pinpoints G83 as the key RNA residue that stimulates GTP hydrolysis. Insertion of G83 into the FtsY active site orients a single glutamate residue provided by Ffh (E277), triggering GTP hydrolysis and complex disassembly at the end of the targeting cycle. The complete conservation of the key residues of the SRP-RNA and the SRP protein implies that the suggested chemical mechanism of GTPase activation is applicable across all kingdoms.
authors.affiliation: ETH Zurich (Swiss Federal Institute of Technology), Institute of Molecular Biology and Biophysics, Zürich 8093, Switzerland.
authors.forename: Felix
authors.initials: F
authors.lastname: Voigts-Hoffmann
authors.affiliation: ETH Zurich (Swiss Federal Institute of Technology), Institute of Molecular Biology and Biophysics, Zürich 8093, Switzerland.
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Schmitz
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
authors.forename: Kuang
authors.initials: K
authors.lastname: Shen
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA. Electronic address: sshan@caltech.edu.
authors.forename: Shu-Ou
authors.initials: SO
authors.lastname: Shan
authors.affiliation: University of Sydney, School of Molecular Bioscience, Sydney, NSW 2006, Australia. Electronic address: sandro.ataide@sydney.edu.au.
authors.forename: Sandro F
authors.initials: SF
authors.lastname: Ataide
authors.affiliation: ETH Zurich (Swiss Federal Institute of Technology), Institute of Molecular Biology and Biophysics, Zürich 8093, Switzerland. Electronic address: ban@mol.biol.ethz.ch.
authors.forename: Nenad
authors.initials: N
authors.lastname: Ban
mesh_terms: D017607:Aluminum Compounds / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D020134:Catalytic Domain / Q000187:drug effects / Q000235:genetics; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D005459:Fluorides / Q000494:pharmacology; D020549:GTP Phosphohydrolase Activators / Q000494:pharmacology; D020558:GTP Phosphohydrolases / Q000235:genetics* / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000235:genetics / Q000378:metabolism; D006868:Hydrolysis / Q000187:drug effects; D008969:Molecular Sequence Data; D012313:RNA / Q000235:genetics* / Q000378:metabolism; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics* / Q000378:metabolism; D017422:Sequence Analysis, DNA; D018271:Signal Recognition Particle / Q000235:genetics* / Q000378:metabolism*
chemical_list: D017607:Aluminum Compounds; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C082931:Ffh protein, E coli; C087406:FtsY protein, Bacteria; D020549:GTP Phosphohydrolase Activators; D012329:RNA, Bacterial; D018160:Receptors, Cytoplasmic and Nuclear; D018271:Signal Recognition Particle; D006153:Guanosine Diphosphate; D012313:RNA; D020558:GTP Phosphohydrolases; D005459:Fluorides; C032311:aluminum fluoride