AtTPR7 is a chaperone-docking protein of the Sec translocon in Arabidopsis.
Chaperone-assisted sorting of post-translationally imported proteins is a general mechanism among all eukaryotic organisms. Interaction of some preproteins with the organellar membranes is mediated by chaperones, which are recognised by membrane-bound tetratricopeptide repeat (TPR) domain containing proteins. We have characterised AtTPR7 as an endoplasmic reticulum protein in plants and propose a potential function for AtTPR7 in post-translational protein import. Our data demonstrate that AtTPR7 interacts with the heat shock proteins HSP90 and HSP70 via a cytosol-exposed TPR domain. We further show by in vitro and in vivo experiments that AtTPR7 is associated with the Arabidopsis Sec63 homologue, AtERdj2. Interestingly, AtTPR7 can functionally complement a Δsec71 yeast mutant that is impaired in post-translational protein transport. These data strongly suggest that AtTPR7 not only has a role in chaperone binding but also in post-translational protein import into the endoplasmic reticulum, pointing to a general mechanism of chaperone-mediated post-translational sorting between the endoplasmic reticulum, mitochondria and chloroplasts in plant cells.
Department of Biology I, Botany, Ludwig-Maximilians-Universität München, Großhaderner Strasse 2-4, D-82152 Planegg-Martinsried,  Germany.
Regina
R
Schweiger
Nina C
NC
Müller
Manfred J
MJ
Schmitt
Jürgen
J
Soll
Serena
S
Schwenkert
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000166:cytology / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism*; D002478:Cells, Cultured; D004721:Endoplasmic Reticulum / Q000378:metabolism; D055786:Gene Knockout Techniques; D005816:Genetic Complementation Test; D006360:Heat-Shock Proteins / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000378:metabolism*; D018832:Molecular Chaperones / Q000737:chemistry / Q000378:metabolism*; D058977:Molecular Sequence Annotation; D008969:Molecular Sequence Data; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D012441:Saccharomyces cerevisiae; D017386:Sequence Homology, Amino Acid; D014026:Nicotiana
D029681:Arabidopsis Proteins; D006360:Heat-Shock Proteins; D026901:Membrane Transport Proteins; D018832:Molecular Chaperones; C561502:OEP61 protein, Arabidopsis