Complete nucleotide sequence and deduced polypeptide sequence of a nonmuscle myosin heavy chain gene from Acanthamoeba: evidence of a hinge in the rodlike tail.
Complete nucleotide sequence and deduced polypeptide sequence of a nonmuscle myosin heavy chain gene from Acanthamoeba: evidence of a hinge in the rodlike tail.
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DOI：
10.1083/jcb.105.2.913
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发表时间：
1987-08
期刊：
影响因子：
--
通讯作者：
Korn ED
中科院分区：
文献类型：
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作者：
Hammer JA 3rd;Bowers B;Paterson BM;Korn ED
我们已经完全测序了编码肌球蛋白II重链的基因，肌球蛋白II是一种来自土壤卡氏阿米巴的非肌肉肌球蛋白。该基因全长6kb，由3个小内含子切割而成，编码1,509个残基的重链多肽。与脊椎动物和无脊椎动物肌肉肌球蛋白基因相比，这三个内含子的位置在很大程度上是保守的。推导的肌球蛋白II球头氨基酸序列与大鼠胚胎骨骼肌和线虫UNC54肌球蛋白的球头序列高度相似。相比之下，没有唯一的方法将推导出的肌球蛋白II杆状氨基酸序列与这些肌肉肌球蛋白的杆状序列进行比对。然而，肌球蛋白II杆序列中疏水残基和带电残基的周期性决定了杆的卷曲结构及其在肌球蛋白细丝中的联系，与肌肉肌球蛋白的周期非常相似。我们得出结论，这种非肌肉肌球蛋白与脊椎动物和无脊椎动物的肌肉肌球蛋白具有共同的祖先重链基因。肌球蛋白II和肌肉肌球蛋白的杆状序列之间的低水平直接序列相似性可能反映了对杆状结构域残基变化的普遍耐受性(只要疏水和带电残基的周期性基本保持不变)，这些肌球蛋白相对进化的“年龄”，以及肌球蛋白II和肌肉肌球蛋白细丝特性之间的特定差异。最后，序列分析和电子显微镜显示，肌球蛋白II棒状尾巴中存在一个定义明确的铰链区，在那里可以发生急剧弯曲。我们推测，该铰链可能在介导重链磷酸化对酶活性的影响中起关键作用。
We have completely sequenced a gene encoding the heavy chain of myosin II, a nonmuscle myosin from the soil ameba Acanthamoeba castellanii. The gene spans 6 kb, is split by three small introns, and encodes a 1,509-residue heavy chain polypeptide. The positions of the three introns are largely conserved relative to characterized vertebrate and invertebrate muscle myosin genes. The deduced myosin II globular head amino acid sequence shows a high degree of similarity with the globular head sequences of the rat embryonic skeletal muscle and nematode unc 54 muscle myosins. By contrast, there is no unique way to align the deduced myosin II rod amino acid sequence with the rod sequence of these muscle myosins. Nevertheless, the periodicities of hydrophobic and charged residues in the myosin II rod sequence, which dictate the coiled-coil structure of the rod and its associations within the myosin filament, are very similar to those of the muscle myosins. We conclude that this ameba nonmuscle myosin shares with the muscle myosins of vertebrates and invertebrates an ancestral heavy chain gene. The low level of direct sequence similarity between the rod sequences of myosin II and muscle myosins probably reflects a general tolerance for residue changes in the rod domain (as long as the periodicities of hydrophobic and charged residues are largely maintained), the relative evolutionary "ages" of these myosins, and specific differences between the filament properties of myosin II and muscle myosins. Finally, sequence analysis and electron microscopy reveal the presence within the myosin II rodlike tail of a well-defined hinge region where sharp bending can occur. We speculate that this hinge may play a key role in mediating the effect of heavy chain phosphorylation on enzymatic activity.