SEQUENCE-ANALYSIS OF MUTATIONS THAT AFFECT THE SYNTHESIS, ASSEMBLY AND ENZYMATIC-ACTIVITY OF THE UNC-54 MYOSIN HEAVY-CHAIN OF CAENORHABDITIS-ELEGANS
SEQUENCE-ANALYSIS OF MUTATIONS THAT AFFECT THE SYNTHESIS, ASSEMBLY AND ENZYMATIC-ACTIVITY OF THE UNC-54 MYOSIN HEAVY-CHAIN OF CAENORHABDITIS-ELEGANS
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DOI：
10.1016/0022-2836(85)90170-6
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发表时间：
1985-01-01
影响因子：
5.6
通讯作者：
WATERSTON, RH
中科院分区：
文献类型：
--
作者：
DIBB, NJ;BROWN, DM;WATERSTON, RH
对线虫UNC-54肌球蛋白H链基因的11个代表性突变进行了测序，这些突变影响编码的肌球蛋白H链的合成、组装或酶活性。在测序的UNC-54突变中，有六个会导致蛋白质合成提前终止。4个突变(e1092、e1115、e1213、e1328)为OchE突变，1个突变(E903)为移码突变，导致邻近的UGA终止子提前终止，1个突变(E190)为缺失，改变了阅读框并导致终止于Ochre密码子。两个突变(e675和s291)处于阶段缺失，导致肌球蛋白杆段缩短。这些异常的肌球蛋白不能组装成正常的粗丝。错义突变(e1152、s74、s95)的序列变化表明，氨基酸残基对肌球蛋白功能至关重要。突变e1152导致肌球蛋白H链的产生不能组装成粗丝。它在杆状结构的末端有2个相邻的氨基酸替换，表明亚片段-2在粗丝组装中发挥了作用。S74或S95的纯合子突变是非常缓慢的，尽管它们使肌球蛋白H链正常组装。S95和S74编码的氨基酸替换在23倍。103兆瓦，50倍。肌球蛋白头部的103 mW结构域，位于ATP结合位点的两侧。测序的突变按照从基因精细结构图谱实验中预测的顺序分布在整个基因中。在甲烷磺酸乙酯诱变后分离到的8个点突变中，有7个是G.cntdot。C到A.cntdot。T跃迁。一个X射线诱导的等位基因被证明是两个相邻胸苷残基的缺失。这3个缺失突变位于肌球蛋白杆状区域，有许多正向和反向核苷酸序列重复，但它们的来源不能用同源重组来解释。相反，对缺失连接的比较表明，缺失是由特定部位的机制引起的。
Representative mutations (11) were sequenced of the unc-54 myosin H chain gene of C. elegans that affect the synthesis, assembly or enzymatic activity of the encoded myosin H chain. Six of the sequenced unc-54 mutations cause premature termination of protein synthesis. Four mutations (e1092, e1115, e1213, e1328) were ochre mutations, 1 mutation (e903) was a frameshift, which caused premature termination at a nearby UGA terminator, and 1 mutation (e190) was a deletion that altered the reading frame and caused termination at an ochre codon. Two mutations (e675 and s291) were in phase deletions, which resulted in a shortened myosin rod segment. These aberrant myosins fail to assemble into normal thick filaments. The sequence alterations of the missense mutations (e1152, s74, s95) indicated amino acid residues that are critical for myosin function. The mutation e1152 causes the production of a myosin H chain that fails to assemble into thick filaments. It had 2 adjacent amino acid substitutions at the extreme amino terminus of the rod, indicating a role for subfragment-2 in thick filament assembly. Mutants homozygous for s74 or s95 are very slow-moving, although they make myosin H chains that assemble normally. The encoded amino acid substitutions of s95 and s74 are in the 23 .times. 103 MW and 50 .times. 103 MW domains of the myosin head, flanking the ATP binding site. The sequenced mutations are distributed throughout the gene in the order predicted from genetic fine-structure mapping experiments. Seven of 8 point mutations isolated following ethyl methanesulfonate mutagenesis were G .cntdot. C to A .cntdot. T transitions. A single X-ray-induced allele proved to be a deletion of 2 adjacent thymidine residues. The 3 deletion mutations were found in a region of the myosin rod with numerous direct and inverted nucleotide sequence repeats, but their origin cannot be accounted for by homologous recombination. Instead, a comparison of the deletion junctions suggests that the deletions arose by a site-specific mechanism.