Abstract
Most chloroplastic proteins are encoded by the nuclear genome and synthesized in the cytosol as precursor proteins with transit peptides at their N-termini and imported into chloroplasts. Precursors are imported through the translocon at the outer and the inner envelope membranes, Toc and Tic, respectively. This process requires ATP at mM order. At the early stage of import, however, precursors are irreversibly bound to the chloroplastic surface to form the translocation intermediate under the limited energy conditions. We have reported that three different translocation intermediates may form under different energy conditions. To further characterize these early translocation intermediates, we have applied the site-specific cross-linking strategy to investigate the interactions between precursors and translocon components. Several cross-linked products have been observed depending on the energy conditions. Our current effort of the cross-linking experiments will be presented at the meeting.
