title: Interaction of transition metal ions with ribonuclease A. II. The selective effects of Mn2+, Zn2+, Cd2+ and Hg2+ on the histidine magnetic resonance.
abstract: Zn2+, Cd2+ and Hg2+ inhibit ribonuclease but Mn2+ does not except at very high concentrations. By high resolution NMR one can detect in the pH range 5-8 the C-2 protons of histidines 105, 12, and 119. The inhibiting ions produce large shifts of the resonance of His-12 but not of His-105. On the other hand Mn2+ broadens the C-2 proton of His-105 much more than it does those of His-12 and 119. The selective shifts suggest that the mechanism of inhibition is binding at or near the active site of which His-12 and 119 are a part. The selective broadening is a consequence of binding of the Mn2+ to a site very far from the active site but closer to His-105.
mesh_terms: D001665:Binding Sites; D002104:Cadmium; D006639:Histidine / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008345:Manganese; D008628:Mercury; D011485:Protein Binding; D011487:Protein Conformation; D012260:Ribonucleases; D015032:Zinc
chemical_list: D002104:Cadmium; D008345:Manganese; D006639:Histidine; D012260:Ribonucleases; D008628:Mercury; D015032:Zinc