title: Toc64--a preprotein-receptor at the outer membrane with bipartide function.
abstract: Protein translocation across membranes is assisted by translocation machineries present in the membrane targeted by the precursor proteins. Translocon subunits can be functionally divided into receptor proteins warranting the specificity of this machine and a translocation channel. At the outer envelope of chloroplasts two sets of receptor proteins regulate protein translocation facing the cytosol or acting in the intermembrane space. One, Toc64 is a receptor of the translocon at the outer envelope of chloroplasts (Toc complex) with dual function. Toc64 recognizes Hsp90 delivered precursor proteins via a cytosolic exposed domain containing three tetratrico-peptide repeat motifs and as demonstrated in here, Toc64 functions also as a major component of a complex facing the intermembrane space. The latter complex is composed of an Hsp70 localized in the intermembrane space, its interaction partner Toc12, a J-domain containing protein and the intermembrane space protein Tic22. We analyzed the intermembrane space domain of Toc64. This domain is involved in preprotein recognition and association with the Toc-complex independent of the cytosolic domain of the Toc64 receptor. Therefore, Toc64 is involved in preprotein translocation across the outer envelope at both sites of the membrane.
authors.affiliation: Botanik, LMU München, Menzinger Str. 67, 80638 München, Germany.
authors.forename: Soumya
authors.initials: S
authors.lastname: Qbadou
authors.forename: Thomas
authors.initials: T
authors.lastname: Becker
authors.forename: Tihana
authors.initials: T
authors.lastname: Bionda
authors.forename: Katharina
authors.initials: K
authors.lastname: Reger
authors.forename: Maike
authors.initials: M
authors.lastname: Ruprecht
authors.forename: Jürgen
authors.initials: J
authors.lastname: Soll
authors.forename: Enrico
authors.initials: E
authors.lastname: Schleiff
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D026901:Membrane Transport Proteins / Q000502:physiology; D008954:Models, Biological; D008969:Molecular Sequence Data; D010447:Peptide Hydrolases / Q000378:metabolism; D010940:Plant Proteins / Q000502:physiology; D011498:Protein Precursors / Q000378:metabolism*; D021381:Protein Transport / Q000502:physiology; D011956:Receptors, Cell Surface / Q000502:physiology; D017386:Sequence Homology, Amino Acid
chemical_list: D029681:Arabidopsis Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D010940:Plant Proteins; D011498:Protein Precursors; D011956:Receptors, Cell Surface; C488374:Toc64 protein, Arabidopsis; D010447:Peptide Hydrolases