Disruption of substrate binding site in E-coli RNA polymerase by lethal alanine substitutions in carboxy terminal domain of the beta subunit

Alanine substitution of four amino acids in two evolutionarily conserved mo tifs, PSRM and RFGEME, near the carboxy terminus of the beta subunit of E, coli RNA polymerase results in a dramatic loss of the enzyme's affinity to substrates with no apparent effect on the maximal rate of the enzymatic rea ction or on binding to promoters. The magnitude and selectivity of the effe ct suggest that the mutations disrupt the substrate binding site of the act ive center. (C) 1999 Federation of European Biochemical Societies.