A mutant Paramecium with a defective calcium-dependent potassium conductance has an altered calmodulin: a nonlethal selective alteration in calmodulin regulation.
A mutant Paramecium with a defective calcium-dependent potassium conductance has an altered calmodulin: a nonlethal selective alteration in calmodulin regulation.
复制标题
具有缺陷的钙依赖性钾电导的突变草履虫具有改变的钙调蛋白：钙调蛋白调节的非致死性选择性改变。
DOI：
10.1073/pnas.84.11.3931
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发表时间：
1987
影响因子：
11.1
通讯作者：
Watterson,DM
中科院分区：
文献类型：
--
作者：
Schaefer,WH;Hinrichsen,RD;Burgess-Cassler,A;Kung,C;Blair,IA;Watterson,DM
草履虫突变体，恐颤A，有一个缺陷，导致体内钙依赖性钾外排通道活性的丧失。将野生型草履虫钙调素微量注射到恐颤A细胞中可以完全纠正这一缺陷，并可通过其他生物的钙调素部分恢复，但不能通过微注射恐颤钙调素来恢复。总的来说，这些结果表明野生型草履虫钙调蛋白具有独特的特征，使其能够完全恢复正常表型，并且恐颤症a中的缺陷可能是改变的钙调蛋白分子。先前的研究建立了野生型钙调素的氨基酸序列，表明草草虫钙调素与其他钙调素有几个不同之处，包括在残基13处存在二甲基赖氨酸。为了直接测试恐颤突变体钙调蛋白可能被改变的可能性，我们纯化了突变体钙调蛋白，并将其与野生型草草虫钙调蛋白进行了比较。我们发现两个草履虫钙调素之间有一个氨基酸序列的差异：突变蛋白在残基101处是苯丙氨酸，而不是丝氨酸。这种变化发生在第三个钙结合环的钙配位残基上。这些和以往的研究表明，钙调素结构的相对细微的变化可以导致体内活性的定量改变，为钙调素在体内的作用和离子通道的调节提供了新的思路，并证明钙调素的功能改变不一定是致命的。
The Paramecium mutant, pantophobiac A, has a defect that results in an in vivo loss of calcium-dependent potassium efflux channel activity. This defect is corrected fully by the microinjection of wild-type Paramecium calmodulin into pantophobiac A cells and is partially restored by calmodulins from other organisms, but it cannot be restored by microinjection of pantophobiac calmodulin. Overall, these results suggested that wild-type Paramecium calmodulin has unique features that allow it to restore fully a normal phenotype and that the defect in pantophobiac A might be an altered calmodulin molecule. Previous studies established the amino acid sequence of wild-type calmodulin and showed that Paramecium calmodulin has several differences from other calmodulins, including the presence of dimethyllysine at residue 13. To test directly the possibility that calmodulin from the pantophobiac mutant might be altered, we purified the mutant calmodulin and compared its properties to those of wild-type Paramecium calmodulin. We found one amino acid sequence difference between the two Paramecium calmodulins: a phenylalanine in the mutant protein, instead of a serine, at residue 101. This change is at a calcium-liganding residue in the third calcium-binding loop. These and previous studies demonstrate that comparatively subtle changes in the structure of calmodulin can result in quantitative alterations in in vivo activity, provide insight into the in vivo roles of calmodulin and the regulation of ion channels, and demonstrate that functional alterations of calmodulin are not necessarily lethal.