ESR study on calcineurin.

Q Wei, F Xiao, J Lu, J Zhou
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Abstract

X-band electron spin resonance spectroscopy was used to investigate the binding of Mn2+ to the apo-forms of calcineurin and its A and B subunits. The results indicated the presence of 2 Mn2+ binding sites of different affinities (20 mumol/L and 60 mumol/L) in the calcineurin A subunit and 4 Mn2+ binding sites in the calcineurin subunit B, 2 high affinity and 2 low affinity binding sites with Kd's of 4 mumol/L and 90 mumol/L, respectively. Interestingly and quite surprisingly, Mn2+ binding to the holoenzyme was characterized by only 2 binding sites with Kd's of 7 mumol/L and 33 mumol/L. However, in the presence of calmodulin about 10 Mn2+ sites were detected, and the Mn2+ calmodulin-calcineurin complex exhibited enzymatic activity. These results, based on direct spectral measurements of the metal ligand, demostrate that Mn2+ binds to both free subunits of calcineurin in a manner distinct from binding to the holoenzyme. Also, the data suggest that conformational changes occur upon heterodimer formation and association of the holoenzyme with the regulatory protein calmodulin.

钙调磷酸酶的ESR研究。
利用x波段电子自旋共振光谱研究了Mn2+与钙调磷酸酶载形体及其A、B亚基的结合。结果表明,钙调神经磷酸酶A亚基存在2个不同亲和力的Mn2+结合位点(20 μ mol/L和60 μ mol/L),钙调神经磷酸酶B亚基存在4个Mn2+结合位点,Kd值分别为4 μ mol/L和90 μ mol/L,具有2个高亲和力和2个低亲和力结合位点。有趣且令人惊讶的是,Mn2+与全酶结合的特征只有2个结合位点,Kd分别为7和33 μ mol/L。然而,在钙调蛋白存在的情况下,检测到大约10个Mn2+位点,并且Mn2+钙调素-钙调神经磷酸酶复合物表现出酶活性。这些结果基于金属配体的直接光谱测量,表明Mn2+以不同于与全酶结合的方式与钙调磷酸酶的两个自由亚基结合。此外,数据表明,在异源二聚体形成和全酶与调节蛋白钙调蛋白结合时,构象发生变化。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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