... the c-phosphate of the bound nucleotide across the dimer [15] and the aromatic residue of the A-loopstacks against the adenine moiety of boundnucleotide and provides further stabilization and specificity ... cleavage of the c-phosphate does occur in the NBD with the mutation at the IC [36,38,39]. More-over, these and other studies suggest that the ICresidues are involved in the formation of the NBDdimer, ... reproducibility of our currentassay; and would represent < 1% of the activity of the wild-type enzyme.We then determined, by photoaffinity labeling,whether any of the mutations altered the apparentbinding...