Tic110 and Tic20: multiple translocation channels at the Tic Translocon?

The Tic complex (Translocon at the inner envelope membrane of chloroplasts) mediates the translocation of nuclear encoded chloroplast proteins across the inner envelope membrane. Tic110 forms one prominent protein translocation channel. Additionally, Tic20, another subunit of the complex, was proposed to form a protein import channel - either together with or independent of Tic110.

Our aim is to compare Tic110 and Tic20, in a comprehensive biochemical and electrophysiological study. Topological analyses with recombinant protein were followed by reconstitution into liposomes, mimicking the in vivo environment of these proteins. After firm insertion into the lipid vesicles was verified, electrophysiological measurements were performed to unveil channel characteristics of Tic110 and Tic20.Furthermore , transcript and protein levels in Arabidopsis thaliana and Pisum sativum were analysed.

Last but not least, two-dimensional gel electrophoresis (Blue Native/SDS) provided clues about the complex formation among Tic110 and Tic20.