Chu, Chiung-chih , Chou, Ming-lun , Chen, Lih-jen , Akita, Mitsuru , Li, Hsou-min .
Stimulation of transit-peptide release and ATP hydrolysis by a cochaperone during protein import into chloroplasts.
Three components of the chloroplast protein translocon, Tic110, Hsp93 (ClpC) and Tic40, have been shown to be important for protein translocation across the inner envelope membrane into the stroma. Here we show the molecular interactions among these three components that facilitate processing and translocation of precursor proteins. Transit-peptide binding by Tic110 recruits Tic40 binding to Tic110, which in turn causes the release of transit peptides from Tic110, freeing the transit peptides for processing. The Tic40 C-terminal domain, which is homologous to the C terminus of co-chaperones Sti1p/Hop and Hip but with no known function, stimulates ATP hydrolysis by Hsp93. Hsp93 dissociates from Tic40 in the presence of ADP, suggesting that Tic40 functions as an ATPase activation protein for Hsp93. Our data suggest that chloroplasts have evolved the Tic40 co-chaperone to increase the efficiency of precursor processing and translocation.
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1 - Academia Sinica, Institute of Molecular Biology
2 - Ehime University Japan, Faculty of Agriculture
3 - Academia Sinica, Institute of Molecular Biology, Nankang, Taipei, 11529, Taiwan
chloroplast protein transport
Presentation Type: ASPB Minisymposium
Location: Continental B/Hilton
Date: Monday, July 9th, 2007
Time: 8:55 AM