Lometto Stefano, Sparvoli Daniela, Malengo Gabriele, Heimerl Thomas, Hochberg Georg K A
Evolutionary Biochemistry Group, Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch-Str. 10, 35043 Marburg, Germany.
Laboratory of Pathogen Host Interactions, UMR5294, Université de Montpellier, INSERM, CNRS, Montpellier, Pl E. Bataillon Bat. 24 2et, CC107, Montpellier 34095, France.
Eur J Protistol. 2024 Oct;96:126121. doi: 10.1016/j.ejop.2024.126121. Epub 2024 Oct 11.
The mitochondrial citrate synthase (mCS) purified from the ciliate Tetrahymena thermophila has been reported to form intermediate-filament-like structures during conjugation and to self-assemble into fibers when recombinantly expressed. This would represent a rare example of a tractable and recent origin of a novel cytoskeletal element. In an attempt to investigate the evolutionary emergence of this behavior, we re-investigated the ability of Tetrahymena's mCS to form filaments in vivo. Using strep-tagged mCS in Tetrahymena and monoclonal antibodies, we found no evidence of filamentous structures during conjugation or starvation. Extensive biochemical characterization of mCS revealed that the self-assembly of recombinant protein is triggered by a specific chemical moiety shared by MES and HEPES buffers used in previous studies. The absence of indicative phenotypes in fiber-deficient GFP-tagged mutants indicates that Tetrahymena mCS did not evolve a structural role in sexual reproduction or metabolic regulation.
据报道，从嗜热四膜虫中纯化出的线粒体柠檬酸合酶（mCS）在接合过程中会形成中间丝样结构，并且在重组表达时会自组装成纤维。这将代表一种新型细胞骨架元件易于处理且起源较新的罕见例子。为了研究这种行为的进化起源，我们重新研究了四膜虫的mCS在体内形成细丝的能力。通过在四膜虫中使用链霉亲和素标签的mCS和单克隆抗体，我们发现在接合或饥饿期间没有丝状结构的证据。对mCS的广泛生化表征表明，重组蛋白的自组装是由先前研究中使用的MES和HEPES缓冲液共有的特定化学部分触发的。在缺乏纤维的绿色荧光蛋白标记突变体中没有指示性表型，这表明四膜虫的mCS在有性生殖或代谢调节中没有进化出结构作用。
