ENHANCEMENT OF TRANSCRIPTIONAL ACTIVITY OF T7 RNA-POLYMERASE BY GUANIDINE-HYDROCHLORIDE

T7 RNA polymerase shows an increase in processive transcription in the presence of low concentrations of guanidine hydrochloride (GdnCl) upt o 60 mM, which is not observed when the enzyme is treated with urea. H igher concentrations of the denaturant lead to a progressive loss in t he processive transcriptional activity of the enzyme. We have attempte d to explain the above phenomenon in terms of the structural change in the enzyme. Fluorescence and CD studies suggest that the tertiary str ucture of the native enzyme undergoes an alteration upon addition of l ow concentration of guanidine hydrochloride. This is also indicated fr om the decreased susceptibility of the enzyme to limited proteotysis b y trypsin. (C) 1998 Federation of European Biochemical Societies.