THE PROTEIN IMPORT APPARATUS OF CHLOROPLASTS

Routing of cytosolically synthesized precursor proteins into chloropla sts in a specific process which involves a multitude of soluble and me mbrane components. In this review we will focus on early events of the translocation pathway of nuclear coded plastidic precursor proteins a nd compare import routes for polypeptides of the outer chloroplast env elope to that of internal chloroplast compartments. A number of protei ns housed in the chloroplast envelopes have been implied to be involve d in the translocation process. but so far a certain function has not been assigned to any of these proteins. The only exception could be an envelope localized hsc 70 homologue which could retain the import com petence of a precursor protein in transit into the organelle.