FIG. 4.

Growth of strains with different translation initiation sites in URH1. Growth was on SC-HIS-LEU supplemented with uracil or uridine, respectively. The positive control strain YZRM22 is prototrophic (URA3 gene on plasmid), and the negative control YZRM64 contains the empty vector (ADH1 promoter only). The constructs complementing the urh1 disruption in strains YZRM28 and YZRM24 start at the first or second ATG; in YZRM67 a frameshift mutation (FS) was introduced between ATG1 and ATG2. The relative uridine hydrolase activity of the strains is indicated (100% = 34 mU/mg of protein).