Allosteric binding of nucleoside triphosphates to RNA polymerase regulatestranscription elongation

The regulation of transcription elongation and termination appears to be go verned by the ability of RNA polymerase elongation complexes to adopt multi ple conformational states; however, the factors controlling the distributio n between these states remain elusive. We used transient-state kinetics to investigate the incorporation of single nucleotides. We demonstrate that E. coli RNA polymerase contains an allosteric binding site in addition to the catalytic site. Binding of the templated nucleoside triphosphate (NTP), bu t not nontemplated NTPs, to this site increases the rate of nucleotide inco rporation. The data suggest that RNA polymerase can exist in a state that c atalyzes synthesis slowly (unactivated) and one that catalyzes synthesis ra pidly (activated), with the transition from the slow to the fast state bein g induced by binding of the templated NTP to the allosteric site.