The vast majority of chloroplast proteins are encoded in the nucleus,
synthesized in the cytosol as precursors with a chloroplast transit
peptide (cTP, indicated in Fig. I as a red rectangle), and guided by the socalled
‘guidance complex’ (not shown) to the Toc/Tic translocon (TT) [a].
After import into the chloroplast the cTP is cleaved by the stromal
processing peptidase (indicated as black scissors)