Traversa U, Rosati A
Department of Biomedical Sciences, University of Trieste, Italy.
Acta Physiol Hung. 1996;84(4):465-7.
The results suggest that: 1) Zinc ions may chelate the histidines critical for the agonist binding preventing hydrogen bonds between nonprotonated nitrogen atom of His-251 and the exocyclic N6-H in CHA or CCPA molecule and between His-278 and -OH of the ribose ring. This mechanism can explain the reduction in the number of binding sites without changing the affinity. 2) Cadmium ions may oxidize cysteine SH-groups. The redox reaction between Cd2+ and receptor thiols may result in binding of the metal into stable (di)thiol-cadmium complexes rather than in the formation of disulfide and liberation of the reduced metal. This mechanism can justify the conformational modifications of the receptor molecule producing the decrease in affinity.
1）锌离子可能螯合对激动剂结合至关重要的组氨酸，从而阻止His-251的非质子化氮原子与CHA或CCPA分子中环外N6-H以及His-278与核糖环的-OH之间形成氢键。该机制可以解释结合位点数量的减少而不改变亲和力。2）镉离子可能氧化半胱氨酸的巯基。Cd2+与受体硫醇之间的氧化还原反应可能导致金属结合形成稳定的（二）硫醇-镉复合物，而不是形成二硫键并释放还原态金属。该机制可以解释受体分子的构象修饰导致亲和力降低的原因。
