Hypertrophic Cardiomyopathy-Linked Mutation D145E Drastically Alters Calcium Binding by the C-Domain of Cardiac Troponin C
Hypertrophic Cardiomyopathy-Linked Mutation D145E Drastically Alters Calcium Binding by the C-Domain of Cardiac Troponin C
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DOI：
10.1021/bi100400h
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发表时间：
2010-06-15
期刊：
影响因子：
2.9
通讯作者：
Tikunova, Svetlana B.
中科院分区：
文献类型：
--
作者：
Swindle, Nicholas;Tikunova, Svetlana B.
心肌肌钙蛋白C的C结构域位点在钙信号调节中的作用尚不清楚。在这项研究中，我们研究了肥厚性心肌病相关突变A8 V，E134 D和D145 E对心肌肌钙蛋白C结构域位点性质的影响。A8 V突变对C结构域位点的钙或镁结合特性基本上没有影响，而突变E134 D适度降低钙和镁结合亲和力。另一方面，D145 E突变影响网站III和IV之间的合作相互作用，显着降低两个网站的钙结合亲和力。心肌肌钙蛋白I锚定区的结合（对应于残基。34-71）与具有D145 E突变的心肌肌钙蛋白C的结合不能恢复与C结构域的正常钙结合。利用荧光疏水探针bis-ANS的实验表明，D145 E突变显著降低了C-结构域钙诱导的疏水暴露的程度。在高非生理钙浓度下，A8 V、E134 D和D145 E突变对心肌肌钙蛋白C对心肌肌钙蛋白I调节区（对应于残基128-180）的亲和力影响最小。相比之下，在较低的生理钙浓度下，D145 E突变导致心肌肌钙蛋白C对心肌肌钙蛋白I调节区的亲和力降低约8倍。我们的研究结果表明，C-域位点的钙结合特性可能对心肌肌钙蛋白C的适当调节功能很重要。
The role of the C-domain sites of cardiac troponin C in the modulation of the calcium signal remains unclear. In this study, we investigated the effects of hypertrophic cardiomyopathy-linked mutations A8V, E134D, and D145E in cardiac troponin Con the properties of the C-domain sites. The A8V mutation had essentially no effect on the calcium or magnesium binding properties of the C-domain sites, while the mutation E134D moderately decreased calcium and magnesium binding affinities. On the other hand, the D145E mutation affected cooperative interactions between sites III and IV, significantly reducing the calcium binding affinity of both sites. Binding of the anchoring region of cardiac troponin I (corresponding to residues. 34-71) to cardiac troponin C with the D145E mutation was not able to recover normal calcium binding to the C-domain. Experiments utilizing the fluorescent hydrophobic probe bis-ANS suggest that the D145E mutation dramatically reduced the extent of calcium-induced hydrophobic exposure by the C-domain. At high nonphysiological calcium concentration, A8V, E134D, and D145E mutations minimally affected the affinity of cardiac troponin C for the regulatory region of cardiac troponin I (corresponding to residues 128-180). In contrast, at lower physiological calcium concentration, the D145E mutation led to an similar to 8-fold decrease in the affinity of cardiac troponin C for the regulatory region of cardiac troponin I. Our results suggest that calcium binding properties of the C-domain sites might be important for the proper regulatory function of cardiac troponin C.