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-Structure paper
タイトル | Rubisco accumulation factor 1 (Raf1) plays essential roles in mediating Rubisco assembly and carboxysome biogenesis. |
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ジャーナル・号・ページ | Proc Natl Acad Sci U S A, Vol. 117, Issue 29, Page 17418-17428, Year 2020 |
掲載日 | 2020年7月21日 |
著者 | Fang Huang / Wen-Wen Kong / Yaqi Sun / Taiyu Chen / Gregory F Dykes / Yong-Liang Jiang / Lu-Ning Liu / |
PubMed 要旨 | Carboxysomes are membrane-free organelles for carbon assimilation in cyanobacteria. The carboxysome consists of a proteinaceous shell that structurally resembles virus capsids and internal enzymes ...Carboxysomes are membrane-free organelles for carbon assimilation in cyanobacteria. The carboxysome consists of a proteinaceous shell that structurally resembles virus capsids and internal enzymes including ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), the primary carbon-fixing enzyme in photosynthesis. The formation of carboxysomes requires hierarchical self-assembly of thousands of protein subunits, initiated from Rubisco assembly and packaging to shell encapsulation. Here we study the role of Rubisco assembly factor 1 (Raf1) in Rubisco assembly and carboxysome formation in a model cyanobacterium, PCC7942 (Syn7942). Cryo-electron microscopy reveals that Raf1 facilitates Rubisco assembly by mediating RbcL dimer formation and dimer-dimer interactions. Syn7942 cells lacking Raf1 are unable to form canonical intact carboxysomes but generate a large number of intermediate assemblies comprising Rubisco, CcaA, CcmM, and CcmN without shell encapsulation and a low abundance of carboxysome-like structures with reduced dimensions and irregular shell shapes and internal organization. As a consequence, the Raf1-depleted cells exhibit reduced Rubisco content, CO-fixing activity, and cell growth. Our results provide mechanistic insight into the chaperone-assisted Rubisco assembly and biogenesis of carboxysomes. Advanced understanding of the biogenesis and stepwise formation process of the biogeochemically important organelle may inform strategies for heterologous engineering of functional CO-fixing modules to improve photosynthesis. |
リンク | Proc Natl Acad Sci U S A / PubMed:32636267 / PubMed Central |
手法 | EM (単粒子) |
解像度 | 4.3 Å |
構造データ | EMDB-10235, PDB-6smh: |
由来 |
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キーワード | PHOTOSYNTHESIS / Rubisco / Rubisco accumulation factor1 / Raf1 / Synechococcus elongatus 7942 / Cyanobacteria |