Effect of Escherichia coli DNA binding protein on the transcription of single-stranded phage M13 DNA by Escherichia coli RNA polymerase

Abstract

E.Coli DNA binding protein strongly inhibits the transcription of single-stranded rather than double-stranded phage M13 DNA by E.Coli RNA polymerase. This inhibition cannot be significantly overcome by increasing the concentration of RNA polymerase. Nor does the order of addition of binding protein affect its inhibitory property: inhibition is evident whether binding protein is added before or after the formation of the RNA polymerase-DNA complex. Inhibition is also observed if binding protein is added at various times after initiation of RNA synthesis. Maximal inhibition occurs at a binding protein-to-DNA ratio (W/W) of about 8:1. This corresponds to one binding protein molecule covering about 30 nucleotides, in good agreement with values obtained by physical measurements.