Bergeron Julien R C, Lale-Farjat Shamar L M, Lewicka Hanna M, Parry Chloe, Kollman Justin M
Randall Centre for Cell and Molecular Biophysics, King's College London, London SE1 1UL, United Kingdom.
Prosemble group LTD, London SE1 1UL, United Kingdom.
Proc Natl Acad Sci U S A. 2025 Mar 18;122(11):e2500913122. doi: 10.1073/pnas.2500913122. Epub 2025 Mar 12.
The cytoskeleton is crucial for cell organization and movement. In Eukaryotes, it largely consists of the protein actin, that forms a double-stranded linear filamentous structure in the presence of ATP and disassemble upon ATP hydrolysis. Bacteria also possess actin homologs, that drive fundamental cellular processes, including cell division, shape maintenance, and DNA segregation. Like eukaryotic actin, bacterial actins assemble into dynamic polymers upon ATP binding, however variation in interactions between strands gives rise to striking diversity of filament architectures. Here, we report a family of bacterial actins of unknown function, conserved among the phylum, which assembles into a unique tubular structure in the presence of ATP. A cryo-EM structure of the filaments reveals that it consists of three strands, unlike other described bacterial actin structures. This architecture provides further insights into the organization of actin-like filaments and has implications for understanding the diversity and evolution of the bacterial cytoskeleton.
细胞骨架对于细胞的组织和运动至关重要。在真核生物中，它主要由蛋白质肌动蛋白组成，肌动蛋白在ATP存在时形成双链线性丝状结构，并在ATP水解时解体。细菌也拥有肌动蛋白同源物，这些同源物驱动基本的细胞过程，包括细胞分裂、形状维持和DNA分离。与真核肌动蛋白一样，细菌肌动蛋白在结合ATP时组装成动态聚合物，然而链间相互作用的差异导致了丝状结构的显著多样性。在这里，我们报道了一类功能未知的细菌肌动蛋白家族，它们在门内保守，在ATP存在时组装成独特的管状结构。丝状结构的冷冻电镜结构显示，它由三条链组成，这与其他已描述的细菌肌动蛋白结构不同。这种结构为肌动蛋白样细丝的组织提供了进一步的见解，并对理解细菌细胞骨架的多样性和进化具有重要意义。
