A Spectroscopic Approach to DNA Transcription and Protein Binding

Poly(purine) · poly(pyrimidine) polymers exist in two forms, one “normal”, the other protonated and called “hysteretic”, both stable at physiological pH. The normal form is well transcribed by Escherichia coli RNA polymerase whereas the protonated form is not. Binding stoichiometries of RNA polymerase and various proteins to poly(dG) · poly(dC) were followed by ultraviolet difference spectroscopy and compared with those obtained with bacteriophage DNAs. The results obtained suggest that the more specific the binding, the more important the hypochromicity is.