Toc12, a novel subunit of the intermembrane space preprotein translocon of chloroplasts.
Translocation of proteins across membranes is essential for the biogenesis of each cell and is achieved by proteinaceous complexes. We analyzed the translocation complex of the intermembrane space from chloroplasts and identified a 12-kDa protein associated with the Toc machinery. Toc12 is an outer envelope protein exposing a soluble domain into the intermembrane space. Toc12 contains a J-domain and stimulates the ATPase activity of DnaK. The conformational stability and the ability to stimulate Hsp70 are dependent on a disulfide bridge within the loop region of the J-domain, suggesting a redox-regulated activation of the chaperone. Toc12 is associated with Toc64 and Tic22. Its J-domain recruits the Hsp70 of outer envelope membrane to the intermembrane space translocon and facilitates its interaction to the preprotein.
Becker
Thomas
T
Botanisches Institut, LMU München, 80638 Munich, Germany.
Hritz
Jozef
J
Vogel
Markus
M
Caliebe
Alexander
A
Bukau
Bernd
B
Soll
Jürgen
J
Schleiff
Enrico
E
D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D001483:Base Sequence; D002462:Cell Membrane / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism / Q000502:physiology*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D004220:Disulfides / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006868:Hydrolysis; D047468:Immunoprecipitation; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology*; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000378:metabolism; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D018532:Pisum sativum / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism; D014176:Protein Biosynthesis; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D017386:Sequence Homology, Amino Acid; D013347:Subcellular Fractions / Q000378:metabolism; D013997:Time Factors; D014158:Transcription, Genetic; D015032:Zinc / Q000378:metabolism
D018076:DNA, Complementary; D004220:Disulfides; D018840:HSP70 Heat-Shock Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D010940:Plant Proteins; C116001:Tic22 protein, Pisum sativum; C406816:Toc64 protein, Pisum sativum; D000255:Adenosine Triphosphate; D010447:Peptide Hydrolases; D015032:Zinc