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首页> 外文期刊>Biochemistry >Conformational Coupling of Mg~(2+) and Ca~(2+) on the Three-State Folding of Calexcitin B
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Conformational Coupling of Mg~(2+) and Ca~(2+) on the Three-State Folding of Calexcitin B

机译：Mg〜（2+）和Ca〜（2+）在Calexcitin B三态折叠中的构象偶联

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摘要

Calexcitin (CE) is a calcium sensor protein that has been implicated in associative learning through the Ca~(2+)-dependent inhibition of K~+ channels and activation of ryanodine receptors. CE_B, the major CE variant, was identified as a member of the sarcoplasmic Ca~(2+) binding protein family: proteins that can bind both Ca~(2+) and Mg~(2+). We have now determined the intrinsic Ca~(2+) and Mg~(2+) binding affinities of CD_B and investigated their interplay on the folding and structure of CD_B. We find that urea denaturation of CE_B displays a three-state unfolding transition consistent with the presence of two structural domains. Through a combination of spectroscopic and denaturation studies we find that on edomain likely possesses molten globule structure and contai9ns a mixed Ca~(2+)/Mg~(2+) binding site and a Ca~(2+) binding site with weak Mg~(2+) antagonism. Furthermore, ion binding to the putative molten globule domain induces native structure formation. The other domain contains a single Ca~(2+)-specific bindign site and has native structure, even in the absence of ion binding. Ca~(2+) binding to CE_B induces the formation of a recessed hydrophobic pocket. On the basis of measured ion binding affinities and intracellular ion concentrations, it appears that Mg~(2+)-CE_B represents the resting state and Ca~(2+)-CE_B corresponds to the active state, under hysiological conditions.
机译：Calexcitin（CE）是一种钙传感器蛋白，已通过依赖Ca〜（2+）的K〜+通道抑制和赖多碱受体的激活而参与了关联学习。 CE_B是主要的CE变异体，被确定为肌浆Ca〜（2+）结合蛋白家族的成员：可以同时结合Ca〜（2+）和Mg〜（2+）的蛋白。现在，我们已经确定了CD_B的固有Ca〜（2+）和Mg〜（2+）结合亲和力，并研究了它们在CD_B折叠和结构上的相互作用。我们发现CE_B的尿素变性显示出与两个结构域的存在一致的三态展开过渡。通过光谱学和变性研究相结合，我们发现在edomain上可能具有熔融的球状结构，并且包含一个混合的Ca〜（2 +）/ Mg〜（2+）结合位点和一个Ca〜（2+）结合位以及弱Mg结合位点。 〜（2+）对抗。此外，离子与假定的熔融球状结构域的结合诱导了天然结构的形成。另一个结构域包含单个Ca〜（2+）特异性结合位点，即使没有离子结合也具有天然结构。 Ca〜（2+）与CE_B的结合诱导了疏水性凹穴的形成。根据测得的离子结合亲和力和细胞内离子浓度，在生理条件下，Mg〜（2 +）-CE_B表示静止状态，而Ca〜（2 +）-CE_B表示活性状态。

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