Complex formation of T7 DNA with RNA polymerase from E. coli B/r WU-36-10-11-12 (E. coli W 12) and its rifampicin-resistant mutant rpoB409 was studied. The rpoB409 mutant possesses a highly pleiotropic effect due to alteration in the RNA polymerase β-subunit structure. The two RNA polymerases have been previously shown to differ in gene selection during RNA synthesis on T7 DNA. In this study it was found that the change in selective properties of the mutant RNA polymerase occurs during its interaction with DNA, the general ability of the enzyme to melt DNA being unaffected.
