Protein import into chloroplasts.

Protein import into chloroplasts is a highly regulated process. The activity of the major import receptors is regulated by protein phosphorylation, as well as by GTP binding and hydrolysis. Complete translocation into the organelle could depend on its redox status, as sensed by the Tic complex. A further possibility is that, upon phosphorylation, precursor proteins form a highly import-competent guidance complex in the cytosol. Hence, several levels of regulation seem to coexist.