On the Binding of tRNA to Escherichia coli RNA Polymerase. Interactions between the Core Enzyme, DNA and tRNA

Abstract

The interplay between the binding of tRNA and DNA to core RNA polymerase was investigated. The monomer core enzyme can bind stably to either DNA or tRNA, whereas the dimer core can fix both DNA and tRNA in a stable ternary complex. The kinetics of the exchange between DNA and tRNA bound to the core enzyme were examined. DNA bound to monomer core can be rapidly displaced by tRNA without prior dissociation of the core from the DNA. Similarly tRNA bound to the core can be displaced by DNA without prior dissociation of the tRNA. The result of Hinkle and Chamberlin that, in contrast, the core enzyme must first dissociate from one DNA molecule before it can transfer to another DNA, was confirmed. As this dissociation is very slow, it is suggested that, in vivo, the tRNA can act as a porter providing the core enzyme with a more kinetically favorable path to transfer from one DNA site to another.