裂殖酵母原肌球蛋白的乙酰化作用并不会促进与同源formin 的差异化结合。
Acetylation of fission yeast tropomyosin does not promote differential association with cognate formins.
机构信息
Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, Vermont, USA.
Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois, USA.
出版信息
Cytoskeleton (Hoboken). 2023 Mar;80(3-4):77-92. doi: 10.1002/cm.21745. Epub 2023 Feb 8.
It was proposed from cellular studies that S. pombe tropomyosin Cdc8 (Tpm) segregates into two populations due to the presence or absence of an amino-terminal acetylation that specifies which formin-mediated F-actin networks it binds, but with no supporting biochemistry. To address this mechanism in vitro, we developed methods for S. pombe actin expression in Sf9 cells. We then employed 3-color TIRF microscopy using all recombinant S. pombe proteins to probe in vitro multicomponent mechanisms involving actin, acetylated and unacetylated Tpm, formins, and myosins. Acetyl-Tpm exhibits tight binding to actin in contrast to weaker binding by unacetylated Tpm. In disagreement with the differential recruitment model, Tpm showed no preferential binding to filaments assembled by the FH1-FH2-domains of two S. pombe formins, nor did Tpm binding have any bias towards the growing formin-bound actin filament barbed end. Although our in vitro findings do not support a direct formin-tropomyosin interaction, it is possible that formins bias differential tropomyosin isoform recruitment through undiscovered mechanisms. Importantly, despite a 12% sequence divergence between skeletal and S. pombe actin, S. pombe myosins Myo2 and Myo51 exhibited similar motile behavior with these two actins, validating key prior findings with these myosins that used skeletal actin.
从细胞研究中提出,由于 S. pombe 原肌球蛋白 Cdc8(Tpm)存在或不存在指定其与哪种形成蛋白介导的 F-肌动蛋白网络结合的氨基末端乙酰化,其会分成两个群体,但没有支持的生物化学。为了在体外解决这个机制,我们开发了 Sf9 细胞中 S. pombe 肌动蛋白表达的方法。然后,我们使用三色彩光 TIRF 显微镜,使用所有重组 S. pombe 蛋白,探测体外涉及肌动蛋白、乙酰化和未乙酰化 Tpm、形成蛋白和肌球蛋白的多成分机制。与较弱的未乙酰化 Tpm 结合相比,乙酰化 Tpm 与肌动蛋白紧密结合。与差异招募模型不一致,Tpm 没有表现出对两种 S. pombe 形成蛋白的 FH1-FH2 结构域组装的丝状肌动蛋白的优先结合,Tpm 结合也没有任何偏向于形成蛋白结合的肌动蛋白丝状末端的生长。虽然我们的体外发现不支持形成蛋白-原肌球蛋白的直接相互作用,但形成蛋白可能通过未发现的机制偏向于差异原肌球蛋白同工型的招募。重要的是,尽管骨骼肌和 S. pombe 肌动蛋白之间存在 12%的序列差异,但 S. pombe 肌球蛋白 Myo2 和 Myo51 与这两种肌动蛋白表现出相似的运动行为,验证了使用骨骼肌肌动蛋白的这些肌球蛋白的先前重要发现。
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