title: The molecular chaperone Hsp90 delivers precursor proteins to the chloroplast import receptor Toc64.
abstract: Precursor protein targeting toward organellar surfaces is assisted by different cytosolic chaperones. We demonstrate that the chloroplast protein translocon subunit Toc64 is the docking site for Hsp90 affiliated preproteins. Thereby, Hsp90 is recognised by the clamp type TPR domain of Toc64. The subsequent transfer of the preprotein from Toc64 to the major receptor of the Toc complex, namely Toc34, is affinity driven and nucleotide dependent. We propose that Toc64 acts as an initial docking site for Hsp90 associated precursor proteins. We outline a mechanism in which chaperones are recruited for a specific targeting event by a membrane-inserted receptor.
authors.affiliation: Botanik, LMU München, München, Germany.
authors.forename: Soumya
authors.initials: S
authors.lastname: Qbadou
authors.forename: Thomas
authors.initials: T
authors.lastname: Becker
authors.forename: Oliver
authors.initials: O
authors.lastname: Mirus
authors.forename: Ivo
authors.initials: I
authors.lastname: Tews
authors.forename: Jürgen
authors.initials: J
authors.lastname: Soll
authors.forename: Enrico
authors.initials: E
authors.lastname: Schleiff
mesh_terms: D000595:Amino Acid Sequence; D002736:Chloroplasts / Q000378:metabolism*; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D018832:Molecular Chaperones / Q000378:metabolism*; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021381:Protein Transport
chemical_list: D018841:HSP90 Heat-Shock Proteins; D008565:Membrane Proteins; D018832:Molecular Chaperones; D010940:Plant Proteins