Phosphorylation motifs in the nonhelical domains of myosin heavy chain and paramyosin may negatively regulate assembly in Caenorhabditis elegans striated muscle.
Phosphorylation motifs in the nonhelical domains of myosin heavy chain and paramyosin may negatively regulate assembly in Caenorhabditis elegans striated muscle.
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肌球蛋白重链和副肌球蛋白非螺旋结构域中的磷酸化基序可能对秀丽隐杆线虫横纹肌中的组装产生负调节。
DOI：
10.1002/cm.20446
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
Reedy,AprilR
中科院分区：
文献类型：
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作者：
Hoppe,PamelaE;Heustis,RonaldJ;Flanagan,KellyA;Reedy,AprilR
我们感兴趣的是建立和维持高度有序的横纹肌收缩装置的机制。肌球蛋白和副肌球蛋白是无脊椎动物粗丝的主要结构成分。在秀丽隐杆线虫中，这两种蛋白都含有一个已知在副肌球蛋白中被磷酸化的同源小非螺旋结构域。在这份报告中，我们发现一个拟议的磷酸化基序(S_S_A)在线虫中高度保守，该基序存在于肌球蛋白和副肌球蛋白的非螺旋区域中。我们使用体内试验来检测蛋白质的组装特性，在这些蛋白质中，一个或多个基序被点突变或缺失作为目标。在所有情况下，突变蛋白的表达改善了相应零突变动物的表型，但产生了各种结构缺陷，包括成年动物的双折射聚集体和胚胎中的异常定位。肌球蛋白A的点突变，但不是缺失，非螺旋尾巴产生了异位结构，在透射电子显微镜下显示为大量杂乱无章的细丝。抗体标记显示，其中一个突变蛋白的聚集体不会招募另一个突变蛋白的内源性版本。对缺乏副肌球蛋白或肌球蛋白A(粗丝中心的基本异构体)的突变胚胎的分析表明，这两种野生型蛋白都可以独立定位和启动组装，尽管产生的结构不正常。我们的结果表明，肌肉细胞通过对S_S_A基序的磷酸化来主动限制肌球蛋白和副肌球蛋白的组装，并且每种蛋白都是独立调节的。©2010 Wiley-Liss公司。
We are interested in mechanisms that establish and maintain the highly ordered contractile apparatus of striated muscle. The homologous proteins myosin and paramyosin are the major structural components of thick filaments in invertebrate animals. InCaenorhabditis elegans, both proteins contain a homologous, small nonhelical domain that is known to be phosphorylated in paramyosin. In this report, we show that a proposed phosphorylation motif (S_S_A), which is present in several copies in the nonhelical regions of both myosin and paramyosin, is highly conserved among nematodes. We used in vivo assays to examine the assembly properties of proteins in which one or more motifs were targeted by point mutagenesis or deletion. In all cases, expression of mutant proteins improved the phenotype of the corresponding null mutant animals, but produced variable structural defects, including birefringent aggregates in adults and abnormal localization in embryos. Point mutation, but not deletion, of the myosin A nonhelical tailpiece produced ectopic structures that appeared as masses of jumbled filaments by TEM. Antibody labeling showed that aggregates of either mutant protein did not recruit the endogenous version of the other. Analysis of mutant embryos lacking either paramyosin or myosin A (the essential isoform at the thick filament center) indicated that both wild‐type proteins can independently localize and initiate assembly, although the structures produced are abnormal. Our results suggest that muscle cells actively restrict myosin and paramyosin assembly through phosphorylation of the S_S_A motifs and that each protein is regulated independently. © 2010 Wiley‐Liss, Inc.