PROPERTIES AND SUBCELLULAR-LOCALIZATION OF A PLASTIDIAL SN-GLYCEROL-3-PHOSPHATE ACYLTRANSFERASE OF PISUM-SATIVUM L EXPRESSED IN ESCHERICHIA-COLI

A full length cDNA encoding the preprotein of the acyl-ACP:sn-glycerol-3-phosphate acyltransferase of pea chloroplasts and two 5'-deletions one of which coded the mature protein and the other a truncated one, were ligated in-frame into the 5'-region of lacZ' of pUC vectors. The resulting constructs were used to transform Escherichia coli cells. All three constructs were expressed in the bacterial cells and polypeptides of molecular masses similar to the expected ones (51, 43 and 38 kDa, respectively) were detected by antibodies against the plastidial acyltransferase. The recombinant mature protein of 43 kDa, which predominantly accumulated in the soluble protein fractions of E. coli, clearly displayed acyltransferase activity. The 38 kDa protein lacking 35 N-terminal amino acids of the mature acyltransferase exhibited no enzymatic activity. The rather unsoluble recombinant preprotein of 51 kDa expressed in E. coli appeared to be inactive as well but it was degradated in vivo to soluble, catalytically active proteins of about 41 kDa which accumulated in the periplasm. The recombinant enzymes expressed in E. coli displayed the same properties as the acyl-transferase of pea chloroplasts including the typical oleate selectivity.