Bacterial microcompartments are protein‐based organelles that carry out specialized metabolic functions in diverse bacteria. Their outer shells are built from several thousand protein subunits. Some of the architectural principles of bacterial microcompartments have been articulated, with lateral packing of flat hexameric BMC proteins providing the basic foundation for assembly. Nonetheless, a complete understanding has been elusive, partly owing to polymorphic mechanisms of assembly exhibited by most microcompartment types. An earlier study of one homologous BMC shell protein subfamily, EutS/PduU, revealed a profoundly bent, rather than flat, hexameric structure. The possibility of a specialized architectural role was hypothesized, but artifactual effects of crystallization could not be ruled out. Here we report a series of crystal structures of an orthologous protein, CutR, from a glycyl‐radical type choline‐utilizing microcompartment from the bacterium Streptococcus intermedius. Depending on crystal form, expression construct, and minor mutations, a range of novel quaternary architectures was observed, including two spiral hexagonal assemblies. A new graphical approach helps illuminate the variations in BMC hexameric structure, with results substantiating the idea that the EutS/PduU/CutR subfamily of BMC proteins may endow microcompartment shells with flexible modes of assembly.

中文翻译：

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用于胆碱利用的细菌微室壳蛋白的对称性破坏和结构多态性。

细菌微区室是基于蛋白质的细胞器，可在多种细菌中执行专门的代谢功能。它们的外壳由数千个蛋白质亚基构成。细菌微室的一些结构原理已经阐明，扁平六聚体 BMC 蛋白的横向堆积为组装提供了基本基础。尽管如此，完整的理解一直难以捉摸，部分原因是大多数微室类型表现出的组装多态机制。对一个同源 BMC 壳蛋白亚家族 EutS/PduU 的早期研究揭示了一种非常弯曲的六聚体结构，而不是扁平的结构。假设了专门的建筑角色的可能性，但不能排除结晶的人为影响。中间链球菌。根据晶体形式、表达构建体和微小突变，观察到了一系列新的四元结构，包括两个螺旋六边形组件。一种新的图形方法有助于阐明 BMC 六聚体结构的变化，结果证实了 BMC 蛋白质的 EutS/PduU/CutR 亚家族可能赋予微室壳以灵活的组装模式的想法。