Secondary structure and thermal stability of caldesmon and its domains.
Secondary structure and thermal stability of caldesmon and its domains.
复制标题
caldesmon及其结构域的二级结构和热稳定性。
DOI：
10.1006/abbi.1993.1554
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发表时间：
1993
影响因子：
3.9
通讯作者：
Jancsó,A
中科院分区：
文献类型：
--
作者：
Graceffa,P;Jancsó,A
肌肉钙调素是一种长而细的蛋白质分子，其N-和C-末端区域由非肌肉钙调素中不存在的中心区域分开。这三个区域似乎是独立的结构域，因为完整肌肉和肝脏钙调素的α-螺旋含量是在宽温度范围内血栓组分片段的α-螺旋含量的总和。根据肝和肌肉caldesmon及其片段的圆二色性光谱，结合二级结构预测算法，估计N-结构域由4 ~ 5个中短α-螺旋组成，中心结构域由一个长的连续α-螺旋伸展组成; C结构域可分为两个亚区，N端C1区含有长α螺旋，C端C2区仅含有无规卷曲。钙调素的热解折叠是逐渐发生的，没有陡峭的过渡，并且在冷却时解折叠是可逆的，这与钙调素已知的“耐热性”一致。这种“状态连续体”展开与许多蛋白质的尖锐、合作、两态展开特征形成对比。随着去折叠程度的增加，caldesmon的结构域也逐渐展开，其顺序为C结构域<完整分子<中心结构域<N结构域，表明caldesmon的热稳定性依次降低。
Muscle caldesmon is a long, thin protein molecule whose N- and C-terminal regions are separated by a central region which is not present in nonmuscle caldesmon. The three regions appear to be independent structural domains since the α-helical content of intact muscle and liver caldesmon is a sum of the α-helical contents of the component thrombic fragments over a broad temperature range. Based on circular dichroism spectra of liver and muscle caldesmon and its fragments, together with secondary structure prediction algorithms, it is estimated that the N-domain consists of a string of four to five short-to-intermediate-length α-helices; the central domain contains a long continuous α-helical stretch; and the C-domain can be divided into two subregions, the N-terminal C1-region, containing a long α-helix, and the C-terminal C2-region, containing only random coil. The thermal unfolding of caldesmon takes place gradually without a steep transition and the unfolding is reversible upon cooling, consistent with the known "heat resistance" of caldesmon. This "continuum-of-states" unfolding contrasts with the sharp, cooperative, two-state unfolding characteristic of many proteins. The domains of caldesmon also unfold gradually with the degree of unfolding increasing in the order C-domain < intact molecule < central domain < N-domain, suggesting that the thermal stability decreases in this order.