Eleven of the codons specifying the amino acids of the flexible catalytic loop [KRRPRPNVAEVM(197–208)] of Bacillus subtilis phosphoribosyl diphosphate synthase have been changed individually to specify alanine. The resulting variant enzyme forms, as well as the wildtype enzyme, were produced in anEscherichia colistrain lacking endogenous phosphoribosyl diphosphate synthase activity and purified to near homogeneity. The B. subtilisphosphoribosyl diphosphate synthase mutant variants K197A and R199A were studied in detail
