THE N-TERMINAL REGION OF MATURE MITOCHONDRIAL ASPARTATE-AMINOTRANSFERASE CAN DIRECT CYTOSOLIC DIHYDROFOLATE-REDUCTASE INTO MITOCHONDRIA IN-VITRO

Two fused genes were constructed which encode for two chimeric protein s in which either 10 or 191 N-terminal amino acids of mature mitochond rial aspartate aminotransferase had been attached to the entire polype ptide chain of cytosolic dihydrofolate reductase. The precursor and ma ture form of mitochondrial aspartate aminotransferase, dihydrofolate r eductase and both chimeric proteins were synthesized in vitro and thei r import into isolated mitochondria was studied. Both chimeric protein s were taken up by isolated organelles, where they became protease res istant, thus indicating the ability of the N-terminal portion of the m ature moiety of the precursor of mitochondrial aspartate aminotransfer ase to direct cytosolic dihydrofolate reductase into mitochondria. (C) 1994 Academic Press, Inc.