Solution structures of the C-terminal domain of cardiac troponin C free and bound to the N-terminal domain of cardiac troponin I
Solution structures of the C-terminal domain of cardiac troponin C free and bound to the N-terminal domain of cardiac troponin I
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DOI：
10.1021/bi9902642
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发表时间：
1999-06-29
期刊：
影响因子：
2.9
通讯作者：
Rosevear, PR
中科院分区：
文献类型：
--
作者：
Gasmi-Seabrook, GMC;Howarth, JW;Rosevear, PR
包含残基33-80且缺乏心脏特异性氨基末端的心肌肌钙蛋白I(cTnI)的N端结构域与包含残基81-161的心肌肌钙蛋白C(cTnC)的C端结构域形成稳定的二元复合物。我们利用异核多维NMR来确定Ca2+饱和cTnC(81-161)的主链和侧链共振，无论是游离的还是与cTnI(33-80)结合的，在游离和cTnI(33-80)结合的cTnC(81-161)确定的二级结构元件之间没有观察到显着差异。我们已经确定了 Ca2+ 饱和的 cTnC(81-161) 游离和与 cTnI(33-80) 结合的溶液结构。虽然 cTnC(81-161) 的三级结构在质量上与溶液中观察到的游离结构类似，但 cTnI(33-80) 的结合主要导致螺旋 F 和 G 之间环区域的结构打开和移动。这些移动共同为 cTnI 的 N 末端结构域提供了结合位点。cTnI(33-80) 的假定结合位点是通过映射酰胺来确定的。 cTnI(33-80) 结合到 C 端 cTnC 结构上诱导质子和氮化学位移变化。正如化学位移变化所表明的，cTnI(33-80) 的结合界面主要涉及位于扩大的疏水口袋中的疏水相互作用。在连接螺旋 F 和 G 的环区域观察到最大的化学位移变化，对可用 TnC 序列的检查表明这些残基高度保守，表明 TnC/TnI 复合物中 Ca2+/Mg2+ 依赖性相互作用位点的共同结合基序。
The N-terminal domain of cardiac troponin I (cTnI) comprising residues 33-80 and lacking the cardiac-specific amino terminus forms a stable binary complex with the C-terminal domain of cardiac troponin C (cTnC) comprising residues 81-161. We have utilized heteronuclear multidimensional NMR to assign the backbone and side-chain resonances of Ca2+-saturated cTnC(81-161) both free and bound to cTnI(33-80), No significant differences were observed between secondary structural elements determined for free and cTnI(33-80)-bound cTnC(81-161). We have determined solution structures of Ca2+-saturated cTnC(81-161) free and bound to cTnI(33-80). While the tertiary structure of cTnC(81-161) is qualitatively similar to that observed free in solution, the binding of cTnI(33-80) results mainly in an opening of the structure and movement of the loop region between helices F and G. Together, these movements provide the binding site for the N-terminal domain of cTnI, The putative binding site for cTnI(33-80) was determined by mapping amide proton and nitrogen chemical shift changes, induced by the binding of cTnI(33-80), onto the C-terminal cTnC structure. The binding interface for cTnI(33-80), as suggested from chemical shift changes, involves predominantly hydrophobic interactions located in the expanded hydrophobic pocket. The largest chemical shift changes were observed in the loop region connecting helices F and G, Inspection of available TnC sequences reveals that these residues are highly conserved, suggesting a common binding motif for the Ca2+/Mg2+-dependent interaction site in the TnC/TnI complex.