Fig. 2. ATPase activity and microtubule binding by salt-bridge mutants. Wild-type and mutant (A) Kar3 and (B) Ncd steady-state ATPase activity in the presence of microtubules; 1 µM motor protein + 0–2 µM microtubules. Wild type (WT; filled circles, —), RA (open circles, —), EA (×, - - -). (C) Microtubule binding by wild-type and mutant Kar3 and Ncd proteins. Coomassie Blue-stained motor protein in the supernatant (unbound) and pellet (microtubule-bound); 1 µM motor protein + 2 µM microtubules, no added nucleotide.