The protein translocon of the plastid envelopes.

The Toc and Tic translocon facilitate import of preproteins into chloroplasts. In the past, it was speculated that several translocon subunits act specifically for different types of precursor proteins or in different tissues. To generate a comprehensive picture of the expression and tissue-specific localization of the translocon subunits, their transcript levels were analyzed in roots and leaves. Certain Tocs and Tics were found to be tissue-specific. The protein composition of the transloci in the envelope membranes of chloroplasts was analyzed to describe the function and possible stoichiometry. In contrast to Tic subunits, several Toc subunits seem to have a high turnover.