Observation of specific interaction of mononucleotides with ribonucleases by nuclear magnetic resonance spectra

Abstract

• 1.

  1. Nuclear magnetic resonance (NMR) spectra were measured to demonstrate the specific interaction of substrates (mononucleotides) with bovine pancreatic ribonuclease I (ribonucleate pyrimidinenucleotido-2′-transferase (cyclizing), EC 2.7.7.16) and Taka-Diastase ribonuclease T₁ (ribonucleate guaninenucleotido-2′-transferase (cyclizing), EC 2.7.7.26).

• 2.

  2. The line widths at half height of certain low field signals exhibited by substrates were taken as a measure of the extent of the interaction.

• 3.

  3. The NMR spectrum of ribonuclease T₁ has been measured and interpreted in the light of its known primary structure for the first time.

• 4.

  4. The spectra of 2′(3′)UMP and uridine were measured in the presence of native ribonuclease I and thermally denaturated ribonuclease I, and it was found that 2′(3′)UMP signals underwent narrowing after heat treatment whereas the spectrum of uridine remained almost unchanged, indicating that only 2′(3′)UMP interacts effectively with the enzyme molecule and that this interaction does not occur after denaturation of the enzyme.