Properties of ATP and UTP Analogues with P‐S‐C5′ Bonds

Abstract

Analogues of ATP and UTP bearing C-5'-S-P ester bonds were found not to be substrates but weak competitive inhibitors of Escherichia coli RNA polymerase. The K-i values of the analogues obtained in the transcription of poly[d(A-T)] or poly(dT) under various conditions are in the order of millimolar. Evidence was derived from proton magnetic resonance spectra that nucleotides with C-5'-S-P bonds do not exist in gauche-gauche conformation normally adopted by natural occurring nucleotides. This leads us to assume that the gauche-gauche conformation is an essental prerequisite for substrates of RNA polymerase. Ado-5'-S-PPP substituted for ATP as substrate of hexokinase from yeast rather effectively thus indicating that a distinct stereochemical orientation of the alpha-phosphate ester bond is not a stringent requirement for substrates of this enzyme.