Functionally important site in the vicinity of the amino-terminus of the Escherichia coli RNA polymerase beta subunit

We have analyzed the interaction of monoclonal antibodies against Escherichia coli RNA polymerase with products of its limited proteolysis. Two major proteolytic fragments of molecular masses 107 and 43 kDa originate as a result of a single cleavage in the vicinity of the 980th amino acid residue. Anti-beta subunit monoclonal antibody PYN-2 inhibiting RNA polymerase activity at the stage of RNA elongation reacts with an epitope located between the amino-terminus and the 50th amino acid residue of the beta subunit. DNA sequencing has shown that the RNA polymerase mutation rpoB22 converts the Gln(1111) codon of the beta subunit gene into the amber codon. An epitope for the monoclonal antibody PYN-6 was located between the major site of proteolytic cleavage and Gln(1111) of the beta subunit.