[Interaction of DNA with RNA-polymerase from Escherichia coli cells infected and uninfected with T2 phage]

RNA polymerase from T2 infected E. coli has greatly reduced activity as compared to the enzyme from uninfected bacteria. Nevertheless both RNA polymerases synthesize heterogenous RNA species with the same maximum corresponding to chain length of 5600 nucleotides on T2 DNA. Rifampicin-challenge experiments suggest that these enzymes have identical kinetics of RNA chain initiation and elongation but their ability to form rapidly starting (RS) and delay starting (I) binary complexes with phage DNA are different. The temperature of I leads to RS transition on T2 DNA is 15 degrees for E. coli holoenzyme, but is 35 degrees for the RNA polymerase from infected cells. The transition temperature depends both on the core and on sigma fraction. Shift temperature technique was developed to investigate the kinetics of I in equilibrium RS complexes rearrangements and their temperature dependence. The rate of these rearrangements is strongly temperature dependent for E. coli holoenzyme, while for RNA polymerase from infected cells it is much lower and is practically temperature independent. From the kinetic data and from the temperature dependence of equilibrium RS-complexes concentration, the rate constants of RS-complexes formation and decay are calculated. The kinetic data obtained in rifampicin challenge experiments are in agreement with the data on the dissociation of DNA-enzyme complexes performed by the filter assay.