title: The structure of the chloroplast signal recognition particle (SRP) receptor reveals mechanistic details of SRP GTPase activation and a conserved membrane targeting site.
abstract: Two GTPases in the signal recognition particle and its receptor (FtsY) regulate protein targeting to the membrane by formation of a heterodimeric complex. The activation of both GTPases in the complex is essential for protein translocation. We present the crystal structure of chloroplast FtsY (cpFtsY) at 1.75 A resolution. The comparison with FtsY structures in different nucleotide bound states shows structural changes relevant for GTPase activation and provides insights in how cpFtsY is pre-organized for complex formation with cpSRP54. The structure contains an amino-terminal amphipathic helix similar to the membrane targeting sequence of Escherichia coli FtsY. In cpFtsY this motif is extended, which might be responsible for the enhanced attachment of the protein to the thylakoid membrane.
authors.affiliation: Biochemie-Zentrum der Universität Heidelberg, INF 328, D-69120, Heidelberg, Germany.
authors.forename: Katharina F
authors.initials: KF
authors.lastname: Stengel
authors.forename: Iris
authors.initials: I
authors.lastname: Holdermann
authors.forename: Klemens
authors.initials: K
authors.lastname: Wild
authors.forename: Irmgard
authors.initials: I
authors.lastname: Sinning
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism; D060365:Chloroplast Proteins; D002736:Chloroplasts / Q000378:metabolism*; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D020558:GTP Phosphohydrolases / Q000737:chemistry* / Q000378:metabolism; D008314:Malonates / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry* / Q000378:metabolism; D018000:Receptors, Peptide / Q000737:chemistry* / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D060365:Chloroplast Proteins; D008314:Malonates; D008565:Membrane Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D018000:Receptors, Peptide; C513946:cpFtsY protein, Arabidopsis; C036318:signal peptide receptor; D020558:GTP Phosphohydrolases