Research Centre of Biotechnology, Russian Academy of Sciences, Moscow, 119071, Russia.
Faculty of Biology, Lomonosov Moscow State University, Moscow, 119991, Russia.
Biochemistry (Mosc). 2023 Jun;88(6):801-809. doi: 10.1134/S0006297923060081.
Tropomyosin (Tpm) is one of the most important partners of actin filament that largely determines its properties. In animal organisms, there are different isoforms of Tpm, which are believed to be involved in the regulation of various cellular functions. However, molecular mechanisms by which various Tpm cytoplasmic regulate of the functioning of actin filaments are still poorly understood. Here, we investigated the properties of Tpm2.1 and Tpm4.1 isoforms and compared them to each other and to more extensively studied Tpm isoforms. Tpm2.1 and Tpm4.1 were very similar in their affinity to F-actin, thermal stability, and resistance to limited proteolysis by trypsin, but differed markedly in the viscosity of their solutions and thermal stability of their complexes with F-actin. The main difference of Tpm2.1 and Tpm4.1 from other Tpm isoforms (e.g., Tpm1.6 and Tpm1.7) was their extremely low thermal stability as measured by the CD and DSC methods. We suggested the possible causes of this instability based on comparing the amino acid sequences of Tpm4.1 and Tpm2.1 with the sequences of Tpm1.6 and Tpm1.7 isoforms, respectively, that have similar exon structure.
原肌球蛋白（Tropomyosin，Tpm）是肌动蛋白丝最重要的伴侣之一，在很大程度上决定了肌动蛋白丝的性质。在动物生物中，存在不同的 Tpm 同工型，据信它们参与了各种细胞功能的调节。然而，各种 Tpm 细胞质同型如何调节肌动蛋白丝的功能的分子机制仍知之甚少。在这里，我们研究了 Tpm2.1 和 Tpm4.1 同工型的性质，并将它们彼此进行了比较，并与研究更为广泛的 Tpm 同工型进行了比较。Tpm2.1 和 Tpm4.1 与 F-肌动蛋白的亲和力、热稳定性和对胰蛋白酶有限水解的抵抗力非常相似，但在溶液的粘度和与 F-肌动蛋白形成复合物的热稳定性方面有明显差异。Tpm2.1 和 Tpm4.1 与其他 Tpm 同工型（例如 Tpm1.6 和 Tpm1.7）的主要区别在于它们的热稳定性极低，这是通过 CD 和 DSC 方法测量得出的。我们根据 Tpm4.1 和 Tpm2.1 的氨基酸序列与具有相似外显子结构的 Tpm1.6 和 Tpm1.7 同工型的序列进行比较，提出了这种不稳定性的可能原因。
