THE N-TERMINAL HYDROPHOBIC REGION OF THE MATURE PHOSPHATE TRANSLOCATOR IS SUFFICIENT FOR TARGETING TO THE CHLOROPLAST INNER ENVELOPE MEMBRANE

To locate the sequence required for directing the phosphate translocat or to the chloroplast inner envelope membrane, a series of chimeric pr oteins constituting parts of the phosphate translocator and the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase, which is n ormally located in the stroma, has been produced. Reciprocal exchanges of the presequences and mature sequences of the phosphate translocato r and the small subunit indicated that the phosphate translocator pres equence contains stromal targeting information and that the mature pro tein is responsible for inner envelope membrane targeting. Chimeric pr oteins containing the N-terminal 46 amino acid residues of the phospha te translocator were directed to the inner envelope membrane. Subdivis ion of this region into its composite hydrophilic and hydrophobic regi ons showed that the hydrophobic region alone, which consists of amino acid residues 24 to 45, was able to direct the small subunit of ribulo se-1,5-bisphosphate carboxylase/oxygenase to the inner envelope membra ne.