In vitro binding of wild-type and mutated Arg80 and Arg80-Mcm1-Arg80 proteins to arginine boxes. The end-labeled 160-bp AluI-AluI DNA fragment containing the ARG5,6 control region was incubated with 10 μg of semipurified yeast extracts (11). Strain 02463dΔARG80 containing pYEP34 (ARG81 LEU2) was transformed with pFL38 (vector; URA3) (lane 1), pFL38-RI (ARG80) (lane 2), pAJ234 (arg80-Y87F-Y110F) (lane 3), pAJ240 (arg80-Y110F-T135S) (lane 4), pAJ239 (arg80-Y110F-T135S-βI swap) (lane 5), pHL13 (Arg80-Mcm1-Arg80) (lane 6), pAJ46 (Arg80-mcm1-N-terminal/βI/αII swap-Arg80) (lane 7), pAJ84 (Arg80-mcm1-N-terminal/αI/βI swap-Arg80) (lane 8), and pAJ85 (Arg80-mcm1-N-terminal/αI/αII swap-Arg80) (lane 9). All of these strains were grown on 1% galactose.