Abstract
Most chloroplast proteins are encoded by the nuclear genome and synthesized in the cytosol as a preprotein which contains an amino-terminal transit peptide. Protein translocation across the outer and inner envelope membranes of chloroplast is mediated by the Toc and Tic complexes, respectively.
We reported previously that pea chloroplast Toc complexes consisting of at least Toc34, Toc75 and Toc159 were migrated at the sizes ranged from 700 to 800kDa on Blue Native PAGE. To elucidate molecular architecture of Toc complexes further, we determined the amount of each Toc component in the isolated chloroplasts and estimated their stoichiometry. Restricted proteolysis of the intact chloroplasts caused partial dissociation of some Toc components and revealed core components of the Toc complex. Also, we have obtained several Arabidopsis mutants of Toc genes. We are currently analyzing whether the mutant Toc complexes show any different molecular architecture as compared to that of the wild-type.
