Lipid phosphorylation in chloroplast envelopes -: Evidence for galactolipid CTP-dependent kinase activities

Lipid phosphorylation takes place within the chloroplast envelope. In addition to phosphatidic acid, phosphatidylinositol phosphate, and their corresponding lyse-derivatives, we found that two novel lipids underwent phosphorylation in envelopes, particularly in the presence of carrier-free [gamma-P-32]ATP, These two lipids incorporated radioactive phosphate in chloroplasts in the presence of [gamma-P-32]ATP or [P-32]P-i and light. Interestingly, these two lipids were preferentially phosphorylated in envelope membranes in the presence [gamma-P-32]CTP, as the phosphoryl donor, or [gamma-P-32]ATP, when supplemented with CDP and nucleoside diphosphate kinase II. The lipid kinase activity involved in this reaction was specifically inhibited in the presence of cytosine 5'-O-(thiotriphosphate) (CTP gamma S) and sensitive to CTP chase, thereby showing that both lipids are phosphorylated by an envelope CTP-dependent lipid kinase. The lipids were identified as phosphorylated galactolipids by using an acid hydrolysis procedure that generated galactose B-phosphate, CTP gamma S did not affect the import of the small ribulose-bisphosphate carboxylase/oxygenase subunit into chloroplasts, the possible physiological role of this novel CTP-dependent galactolipid kinase activity in the chloroplast envelope is discussed.