TRANSFER OF A CHLOROPLAST-BOUND PRECURSOR PROTEIN INTO THE TRANSLOCATION APPARATUS IS IMPAIRED AFTER PHOSPHOLIPASE-C TREATMENT

We have studied the influence of phospholipase C treatment of intact purified chloroplast on the translocation of a plastid destined precursor protein. Under standard import conditions, i.e. in the light in the presence of 2 mM ATP translocation was completely abolished but binding was observed at slightly elevated levels. An experimental regime which allowed binding but not import of the precursor protein, i.e. in the dark in the presence of 10-mu-M ATP, demonstrated that translocation intermediates, normally detected at this stage, were missing in phospholipase treated chloroplasts. The precursor was completely sensitive to protease treatment, indicating that the transfer of the precursor from the receptor to the import apparatus was blocked by phospholipase treatment.