Tropomyosin (Tpm) is an extended α-helical coiled-coil homodimer that regulates actinomyosin interactions in muscle. Molecular simulations of four Tpms, two from the vertebrate class Mammalia (rat and pig), and two from the invertebrate class Malacostraca (shrimp and lobster), showed that despite extensive sequence and structural homology across metazoans, dynamic behavior-particularly long-range structural fluctuations-were clearly distinct. Vertebrate Tpms were more flexible and sampled complex, multi-state conformational landscapes. Invertebrate Tpms were more rigid, sampling a highly constrained harmonic landscape. Filtering of trajectories by principle component analysis into essential subspaces showed significant overlap within but not between phyla. In vertebrate Tpms, hinge-regions decoupled long-range interhelical motions and suggested distinct domains. In contrast, crustacean Tpms did not exhibit long-range dynamic correlations-behaving more like a single rigid rod on the nanosecond time scale. These observations suggest there may be divergent mechanisms for Tpm binding to actin filaments, where conformational flexibility in mammalian Tpm allows a preorganized shape complementary to the filament surface, and where rigidity in the crustacean Tpm requires concerted bending and binding.

中文翻译：

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原肌球蛋白在脊椎动物和无脊椎动物中的比较动力学。

Tropomyosin（Tpm）是一种扩展的α-螺旋卷曲螺旋均二聚体，可调节肌肉中的放线菌素相互作用。四个Tpms的分子模拟，其中两个来自脊椎动物类Mammalia（大鼠和猪），另外两个来自无脊椎动物类Malacostraca（虾和龙虾），显示尽管后生动物具有广泛的序列和结构同源性，但它们的动态行为特别是远距离结构波动明显不同。脊椎动物Tpms更加灵活，并采样了复杂的多状态构象景观。无脊椎动物的Tpm更加刚性，采样了高度受限的谐波景观。通过主成分分析将轨迹过滤到必要的子空间中，在门内（而不是门之间）有明显的重叠。在脊椎动物的Tpms中，铰链区域解耦了远程螺旋运动，并建议了不同的域。相比之下，甲壳类动物Tpms并没有表现出长期的动态相关性，更像是纳秒级的单个刚性棒。这些观察表明，TPM与肌动蛋白丝的结合可能存在不同的机制，其中哺乳动物Tpm的构象柔韧性允许与丝表面互补的预组织形状，而甲壳类动物Tpm的刚性要求一致的弯曲和结合。