CUMULATIVE EFFECTS OF MUTATIONS IN NEWLY SYNTHESIZED MITOCHONDRIAL ASPARTATE-AMINOTRANSFERASE ON UPTAKE INTO MITOCHONDRIA

Mutant genes were constructed which coded for the precursor form of mi tochondrial aspartate aminotransferase in which residue cysteine 166 w as mutated to either serine or alanine and or forms of the protein lac king both the presequence and residues 1-9 of the mature protein but c arrying the same cysteine mutations. The protein products of all of th ese mutant genes were imported into mitochondria that had been added t o the expression system but with varying degrees of efficiency. The re sults showed that the effects of mutation of cysteine 166 and of delet ion of residues 1-9 of the mature protein on sequestration into mitoch ondria were essentially cumulative, suggesting that these parts of the protein are involved in distinct steps on the recognition/uptake path way. (C) 1995 Academic Press, Inc.