Distribution and structure-function relationship of myosin heavy chain isoforms in the adult mouse heart
Distribution and structure-function relationship of myosin heavy chain isoforms in the adult mouse heart
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DOI：
10.1074/jbc.m704574200
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发表时间：
2007-08-17
影响因子：
4.8
通讯作者：
Robbins, Jeffrey
中科院分区：
文献类型：
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作者：
Krenz, Maike;Sadayappan, Sakthivel;Robbins, Jeffrey
两种心肌肌球蛋白重链异构体α和β表现出不同的功能特征，因此可能在心脏内局部分布，以满足特定区域的功能需求。在主要表达α -肌球蛋白重链的成年小鼠心脏中，我们观察到在乳头肌的尖端和靠近瓣膜环的基部等不同区域有高浓度的β -肌球蛋白。鉴于这些不同的肌凝蛋白异构体的分布模式，我们随后探索了肌凝蛋白的异构体特异性结构功能关系。β -和β -异构体在氨基酸序列上有93%相同，但尚不清楚哪些不相同的残基决定了异构体的功能。我们假设位于肌凝蛋白头部肌动蛋白结合界面内或附近的残基影响肌动蛋白结合，从而调节肌动蛋白激活的atp酶活性。嵌合肌球蛋白在-主链中含有从417到682氨基酸的-序列。在小鼠中，大约70%的内源性心脏蛋白被嵌合肌球蛋白取代。含有嵌合肌球蛋白的肌原纤维显示atp酶活性被抑制到在心脏中观察到的水平，表达类似于70%的β -肌球蛋白。体外运动实验表明，嵌合肌凝蛋白产生的肌动蛋白丝滑动速度与β -肌凝蛋白相似，几乎是β -肌凝蛋白的两倍。这些数据表明，这种大结构域序列开关赋予了嵌合肌凝蛋白β样肌动蛋白激活的atp酶活性，表明该区域负责这些肌凝蛋白同工型的独特水解特性。
The two cardiac myosin heavy chain isoforms, alpha and beta, exhibit distinct functional characteristics and therefore may be distributed regionally within the heart to match the functional demands of a specific region. In adult mouse hearts, which predominantly express alpha- myosin heavy chain, we observed high concentrations of beta- myosin in distinct areas such as at the tip of papillary muscles and at the base close to the valvular annulus. In light of these distinct distribution patterns of the myosin isoforms, we subsequently explored the isoform- specific structure function relationships of the myosins. The beta- and beta- isoforms are 93% identical in amino acid sequence, but it remains unclear which of the nonidentical residues determines isoform functionality. We hypothesized that residues situated within or close to the actin- binding interface of the myosin head influence actin binding and thereby modulate actin- activated ATPase activity. A chimeric myosin was created containing beta- sequence from amino acid 417 to 682 within the beta- backbone. In mice, similar to 70% of the endogenous cardiac protein was replaced with the chimeric myosin. Myofibrils containing chimeric myosin exhibited ATPase activities that were depressed to the levels observed in hearts expressing similar to 70% beta- myosin. In vitro motility assays showed that the actin filament sliding velocity generated by chimeric myosin was similar to that of beta- myosin, almost twice the velocities observed with beta- myosin. These data indicate that this large domain sequence switch conferred beta- like actin- activated ATPase activities to the chimeric myosin, suggesting that this region is responsible for the distinct hydrolytic properties of these myosin isoforms.