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首页> 外文期刊>Biochemistry >RELATIONSHIP BETWEEN STABILITY AND FUNCTION FOR ISOLATED DOMAINS OF TROPONIN C
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RELATIONSHIP BETWEEN STABILITY AND FUNCTION FOR ISOLATED DOMAINS OF TROPONIN C

机译：肌钙蛋白C隔离域的稳定性与功能之间的关系

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摘要

Results of spectroscopic thermal and chemical denaturation studies and calcium binding studies are presented for a series of five recombinant chicken troponin C fragments. They were designed to assess the effects of domain isolation, N-helix, and D/E linker helix on stability and calcium affinity. Four of the fragments include the N-terminal regulatory domain and one the C-terminal domain. For the regulatory domain, deletion of the N-helix or the D/E linker decreases the stability of the apo form as measured by Delta G(N-->U,25)degrees. Separation of the domains also decreases the stability. Differences in values of Delta G(N-->U,25)degrees derived from urea and guanidine hydrochloride studies allowed an estimation of the electrostatic component of the free energy of unfolding. Our measurements provide the first quantitative estimate of the stability for the apo-C-domain (Delta G(N-->U,25)degrees = -1.8 kcal/mol) which was obtained using the interaction free energy formalism of Schellman. There is an inverse correlation between calcium affinity, binding cooperativity, and stability for all of these homologously structured fragments. The calcium affinity and cooperativity are highest for the unstructured C-domain and lowest for the N-domain which has the highest stability. In view of the direct effects on the folding stability of the apo-N-domain, the N-helix and the bilobed domain organization of TnC are necessarily involved in the fine-tuning of the affinity and cooperativity of calcium binding. Though not directly involved in calcium coordination, these structural features are important for signal transmission by troponin C in the troponin complex.
机译：提出了一系列五个重组鸡肌钙蛋白C片段的光谱热化学变性研究和钙结合研究的结果。他们旨在评估域隔离，N螺旋和D / E接头螺旋对稳定性和钙亲和力的影响。片段中的四个包括N端调节域，一个C端域。对于调节域，N-螺旋或D / E接头的缺失降低了载脂蛋白形式的稳定性，如Delta G（N-> U，25）度所测量。域的分离也降低了稳定性。从尿素和胍盐酸盐研究得出的Delta G（N-> U，25）度值的差异允许估算展开自由能的静电成分。我们的测量为载脂蛋白C结构域的稳定性提供了第一个定量估计（ΔG（N-> U，25）度= -1.8 kcal / mol），这是使用谢尔曼的相互作用自由能形式学获得的。对于所有这些同源结构片段，钙亲和力，结合协同作用和稳定性之间存在反相关关系。钙亲和力和协同性对于非结构化的C-结构域最高，而对于具有最高稳定性的N-结构域最低。考虑到对载脂蛋白-N结构域的折叠稳定性的直接影响，TnC的N-螺旋和双叶结构域组织必然参与钙结合的亲和力和协同性的微调。尽管不直接参与钙配位，但这些结构特征对于肌钙蛋白复合物中肌钙蛋白C的信号传递非常重要。

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