McKay R T, Pearlstone J R, Corson D C, Gagné S M, Smillie L B, Sykes B D
MRC Group in Protein Structure and Function, Department of Biochemistry, University of Alberta, Canada.
Biochemistry. 1998 Sep 8;37(36):12419-30. doi: 10.1021/bi9809019.
The structure of the regulatory domain of chicken skeletal troponin-C (residues 1-90) when complexed with the major inhibitory region (residues 96-148) of chicken skeletal troponin-I was determined using multinuclear, multidimensional NMR spectroscopy. This complex represents the first interaction formed between the regulatory domain of troponin-C and troponin-I after calcium binding in the regulation of muscle contraction. The stoichiometry of the complex was determined to be 1:1, with a dissociation constant in the 1-40 microM range. The structure of troponin-C in the complex was calculated from 1039 NMR distance and 111 dihedral angle restraints. When compared to the structure of this domain in the calcium saturated "open" form but in the absence of troponin-I, the bound structure appears to be slightly more "closed". The troponin-I peptide-binding site was found to be in the hydrophobic pocket of calcium saturated troponin-C, using edited/filtered NMR experiments and chemical shift mapping of changes induced in the regulatory domain upon peptide binding. The troponin-I peptide (residues 96-148) was found to bind to the regulatory domain of troponin-C very similarly, but not identically, to a shorter troponin-I peptide (region 115-131) thought to represent the major interaction site of troponin-I for this domain of troponin-C.
利用多核多维核磁共振光谱法测定了鸡骨骼肌肌钙蛋白C（1 - 90位氨基酸残基）的调节结构域与鸡骨骼肌肌钙蛋白I的主要抑制区域（96 - 148位氨基酸残基）形成复合物时的结构。该复合物代表了在肌肉收缩调节过程中钙结合后，肌钙蛋白C的调节结构域与肌钙蛋白I之间形成的首次相互作用。确定该复合物的化学计量比为1:1，解离常数在1 - 40微摩尔范围内。根据1039个核磁共振距离约束和111个二面角约束计算出复合物中肌钙蛋白C的结构。与钙饱和“开放”形式但不存在肌钙蛋白I时该结构域的结构相比，结合后的结构似乎稍微更“封闭”一些。通过编辑/过滤核磁共振实验以及肽结合后调节结构域中诱导变化的化学位移图谱，发现肌钙蛋白I的肽结合位点位于钙饱和肌钙蛋白C的疏水口袋中。发现肌钙蛋白I肽（96 - 148位氨基酸残基）与肌钙蛋白C的调节结构域的结合方式非常相似，但并不完全相同，与一个较短的肌钙蛋白I肽（115 - 131区域）类似，该短肽被认为代表了肌钙蛋白I与肌钙蛋白C这一结构域的主要相互作用位点。
