The mechanisms that ensure proper assembly, activity, and turnover of myosin II filaments are fundamental to a diverse range of cellular processes. In Caenorhabditis elegans striated muscle, thick filaments contain two myosins that are functionally distinct and spatially segregated. Using transgenic double mutants, we demonstrate that the ability of increased myosin A expression to restore muscle structure and movement in myosin B mutants requires UNC-82/NUAK kinase activity. Myosin B function appears unaffected in the kinase-impaired unc-82(e1220) mutant: the recessive antimorphic effects on early assembly of paramyosin and myosin A in this mutant are counteracted by increased myosin B expression and exacerbated by loss of myosin B. Using chimeric myosins and motility assays, we mapped the region of myosin A that requires UNC-82 activity to a 531-amino-acid region of the coiled-coil rod. This region includes the 264-amino-acid Region 1, which is sufficient in chimeric myosins to rescue the essential filament-initiation function of myosin A, as well as two sites that interact with myosin head domains in the Interacting Heads Motif. A specific physical interaction between myosin A and UNC-82::GFP is supported by GFP labeling of ectopic myosin A filaments but not thin filaments. We hypothesize that UNC-82 regulates assembly competence of myosin A during parallel assembly in the filament arms.

中文翻译：

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肌球蛋白 A 需要 UNC-82/NUAK 激酶，但肌球蛋白 B 不需要，才能在秀丽隐杆线虫横纹肌的粗丝臂中组装和发挥作用

确保肌球蛋白 II 丝的正确组装、活性和周转的机制是多种细胞过程的基础。在秀丽隐杆线虫横纹肌中，粗丝含有两种功能不同且空间隔离的肌球蛋白。使用转基因双突变体，我们证明增加肌球蛋白 A 表达以恢复肌球蛋白 B 突变体的肌肉结构和运动的能力需要 UNC-82/NUAK 激酶活性。在激酶受损的unc-82(e1220)突变体中，肌球蛋白 B 功能似乎不受影响：该突变体中副肌球蛋白和肌球蛋白 A 早期组装的隐性反形态效应被肌球蛋白 B 表达增加所抵消，并因肌球蛋白 B 缺失而加剧。肌球蛋白和运动测定中，我们将需要 UNC-82 活性的肌球蛋白 A 区域映射到卷曲螺旋杆的 531 个氨基酸区域。该区域包括 264 个氨基酸的区域 1（在嵌合肌球蛋白中足以挽救肌球蛋白 A 的基本丝起始功能），以及与相互作用头基序中的肌球蛋白头结构域相互作用的两个位点。异位肌球蛋白 A 丝（而非细丝）的 GFP 标记支持肌球蛋白 A 和 UNC-82::GFP 之间的特定物理相互作用。我们假设 UNC-82 在丝臂平行组装过程中调节肌球蛋白 A 的组装能力。