Randall Centre for Cell and Molecular Biophysics, King's College London, London, UK.
Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool, UK.
Structure. 2023 Jun 1;31(6):677-688.e4. doi: 10.1016/j.str.2023.03.008. Epub 2023 Apr 3.
Carboxysomes are proteinaceous bacterial microcompartments that sequester the key enzymes for carbon fixation in cyanobacteria and some proteobacteria. They consist of a virus-like icosahedral shell, encapsulating several enzymes, including ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO), responsible for the first step of the Calvin-Benson-Bassham cycle. Despite their significance in carbon fixation and great bioengineering potentials, the structural understanding of native carboxysomes is currently limited to low-resolution studies. Here, we report the characterization of a native α-carboxysome from a marine cyanobacterium by single-particle cryoelectron microscopy (cryo-EM). We have determined the structure of its RuBisCO enzyme, and obtained low-resolution maps of its icosahedral shell, and of its concentric interior organization. Using integrative modeling approaches, we have proposed a complete atomic model of an intact carboxysome, providing insight into its organization and assembly. This is critical for a better understanding of the carbon fixation mechanism and toward repurposing carboxysomes in synthetic biology for biotechnological applications.
羧基体是一种蛋白细菌微室，将固碳的关键酶隔离在蓝细菌和一些 Proteobacteria 中。它们由类似病毒的二十面体壳组成，包含几种酶，包括核酮糖 1,5-二磷酸羧化酶/加氧酶（RuBisCO），负责卡尔文-本森-巴斯汉姆循环的第一步。尽管它们在固碳方面具有重要意义，并且具有巨大的生物工程潜力，但对天然羧基体的结构理解目前仅限于低分辨率研究。在这里，我们通过单颗粒冷冻电镜（cryo-EM）来描述一种海洋蓝细菌的天然α-羧基体。我们确定了其 RuBisCO 酶的结构，并获得了其二十面体壳和同心内部组织的低分辨率图谱。通过整合建模方法，我们提出了一个完整的羧基体原子模型，深入了解其组织和组装。这对于更好地理解固碳机制以及在合成生物学中重新利用羧基体进行生物技术应用至关重要。
