FIG. 1.
Arg8p must be present in the mitochondrial matrix to participate in arginine biosynthesis. The top two panels show the growth of yeast strains on glucose medium (SD) that either contains Arg (Min + Arg) or lacks Arg (Min − Arg). The bottom panel is a Western blot of total-cell extracts probed with anti-Arg8p antibody. The position of Arg8p in the gel is indicated. Lanes: 1, wild-type ARG8 strain with wild-type mtDNA (JKR102); 2, arg8::hisG strain with wild-type mtDNA (DFS188); 3, arg8::hisG strain with wild-type mtDNA (DFS188) transformed with a nuclear 2 μm expression plasmid bearing a truncated ARG8 gene that lacks the N-terminal 21 codons and thus the mitochondrial targeting sequence (pSH303; see Materials and Methods); 4, arg8::hisG strain whose mtDNA contains a truncated ARG8m gene in place of the COX2 coding sequence (SH40). Mitochondrial expression of this gene produces the same protein as in lane 3 but within mitochondria.