Fan S, Bersohn R
Biochim Biophys Acta. 1975 Aug 26;397(2):405-11. doi: 10.1016/0005-2744(75)90129-1.
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.
锌离子、镉离子和汞离子会抑制核糖核酸酶，但锰离子不会，除非浓度非常高。通过高分辨率核磁共振，在pH值为5至8的范围内，可以检测到组氨酸105、12和119的C-2质子。抑制性离子会使组氨酸12的共振发生大幅位移，但不会使组氨酸105的共振发生位移。另一方面，锰离子使组氨酸105的C-2质子的谱线变宽的程度远大于组氨酸12和119的C-2质子。选择性位移表明抑制机制是在活性位点或其附近结合，而组氨酸12和119是该活性位点的一部分。选择性谱线变宽是锰离子与一个距离活性位点很远但更靠近组氨酸105的位点结合的结果。
