Tropomyosin and cofilin are involved in the regulation of actin filament dynamic polymerization and depolymerization. Binding of cofilin changes actin filaments structure, leading to their severing and depolymerization. Non-muscle tropomyosin isoforms were shown before to differentially regulate the activity of cofilin 1; products of TPM1 gene stabilized actin filaments, but products of TPM3 gene promoted cofilin-dependent severing and depolymerization. Here, conformational changes at the longitudinal and lateral interface between actin subunits resulting from tropomyosin and cofilin 1 binding were studied using skeletal actin and yeast wild type and mutant Q41C and S265C actins. Cross-linking of F-actin and fluorescence changes in F-actin labeled with acrylodan at Cys41 (in D-loop) or Cys265 (in H-loop) showed that tropomyosin isoforms differentially regulated cofilin-induced conformational rearrangements at longitudinal and lateral filament interfaces. Tryptic digestion of F-Mg-actin confirmed the differences between tropomyosin isoforms in their regulation of cofilin-dependent changes at actin-actin interfaces. Changes in the fluorescence of AEDANS attached to C-terminal Cys of actin, as well as FRET between Trp residues in actin subdomain 1 and AEDANS, did not show differences in the conformation of the C-terminal segment of F-actin in the presence of different tropomyosins ± cofilin 1. Therefore, actin's D- and H-loop are the sites involved in regulation of cofilin activity by tropomyosin isoforms.

中文翻译：

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肌球蛋白同工型通过调节肌动蛋白丝构象来调节cofilin 1活性。

Tropomyosin和cofilin参与肌动蛋白丝动态聚合和解聚的调节。肌动蛋白丝的结合改变了肌动蛋白丝的结构，导致它们的切断和解聚。非肌肉原肌球蛋白同工型之前显示差异调节cofilin 1的活性。TPM1基因的产物稳定肌动蛋白丝，但TPM3基因的产物促进依赖cofilin的切断和解聚作用。在这里，研究了使用肌动蛋白和酵母野生型以及突变型Q41C和S265C肌动蛋白研究了由原肌球蛋白和cofilin 1结合导致的肌动蛋白亚基之间纵向和横向界面的构象变化。F-肌动蛋白的交联和在Cys41（在D环中）或Cys265（在H环中）用丙烯酰胺标记的F-肌动蛋白的荧光变化表明，原肌球蛋白同工型在纵向和横向丝界面上差异性调节了cofilin诱导的构象重排。 。F-Mg-肌动蛋白的胰蛋白酶消化证实了原肌球蛋白同工型之间在肌动蛋白-肌动蛋白界面上对cofilin依赖性变化的调节中的差异。肌动蛋白C端Cys上附着的AEDANS荧光的变化以及肌动蛋白亚结构域1和AEDANS中Trp残基之间的FRET均未显示在存在肌动蛋白的情况下F-actin的C端片段的构象有差异原肌球蛋白±cofilin1。因此，肌动蛋白的D环和H环是原肌球蛋白同工型调节cofilin活性的位点。