Tropomyosin (Tpm) is an α-helical coiled-coil actin-binding protein playing an essential role in the regulation of muscle contraction. The α- (Tpm 1.1) and γ- (Tpm 3.12) Tpm isoforms are expressed in fast and slow human skeletal muscles, respectively, while β-Tpm (Tpm 2.2) is expressed in both muscle types. This results in the formation of Tpm αα- and γγ-homodimers as well as αβ- and γβ-heterodimers. The properties of αα-homodimer are well studied, whereas very little is known about the functional properties of γγ-homodimer and γβ-heterodimer. We investigated interaction characteristics of Tpm γγ-homodimer and γβ-heterodimer with actin filaments and Ca2+-regulation of actin-myosin interaction on myosin from fast and slow skeletal muscles. The results showed that complexes formed by γγ-Tpm and γβ-Tpm with F-actin are more stable than those with αα-Tpm and αβ-Tpm. The maximum sliding speed of regulated thin filaments with either γγ-Tpm or γβ-Tpm moving over skeletal myosin was significantly less than that of the filaments with αα-Tpm or αβ-Tpm. The results indicate that isoforms of Tpm along with isoforms of myosin determine of functional properties of skeletal muscles and support an idea on the combined expression of myosin and Tpm isoforms.

中文翻译：

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慢速骨骼肌原肌球蛋白的独特功能特性。

Tropomyosin（Tpm）是一种α螺旋卷曲螺旋肌动蛋白结合蛋白，在调节肌肉收缩中起重要作用。α-（Tpm 1.1）和γ-（Tpm 3.12）Tpm亚型分别在快速和慢速人骨骼肌中表达，而β-Tpm（Tpm 2.2）在两种肌肉类型中表达。这导致形成Tpmα-和γ-同二聚体以及α-和γβ-同二聚体。对αα-同二聚体的性质进行了很好的研究，而对γγ-同二聚体和γβ-异二聚体的功能性质知之甚少。我们研究了Tpmγ-同二聚体和γβ-异二聚体与肌动蛋白丝的相互作用特性以及Ca2 +调节快，慢骨骼肌肌球蛋白对肌动蛋白-肌球蛋白相互作用的作用。结果表明，由γ-Tpm和γβ-Tpm与F-肌动蛋白形成的复合物比与αα-Tpm和αβ-Tpm形成的复合物更稳定。γ-Tpm或γβ-Tpm在骨骼肌球蛋白上移动的调节细丝的最大滑动速度明显小于αα-Tpm或αβ-Tpm的细丝的最大滑动速度。结果表明，TPM的同工型与肌球蛋白的同工型一起决定了骨骼肌的功能特性，并支持关于肌球蛋白和Tpm的同工型联合表达的想法。