8WXB

Cryo-EM structure of the alpha-carboxysome shell vertex from Prochlorococcus MED4

Summary for 8WXB

• Entry DOI: 10.2210/pdb8wxb/pdb
• EMDB information: 37902
• Descriptor: Carboxysome shell vertex protein CsoS4A, Major carboxysome shell protein CsoS1, Carboxysome assembly protein CsoS2 (3 entities in total)
• Functional Keywords: alpha-carboxysome, carbon fixation, photosynthesis
• Biological source: Prochlorococcus sp. MED4; More
• Total number of polymer chains: 51
• Total formula weight: 655845.46

Authors

Jiang, Y.L.,Zhou, R.Q.,Zhou, C.Z.,Zeng, Q.L. (deposition date: 2023-10-28, release date: 2024-01-31, Last modification date: 2024-10-30)

Primary citation

Zhou, R.Q.,Jiang, Y.L.,Li, H.,Hou, P.,Kong, W.W.,Deng, J.X.,Chen, Y.,Zhou, C.Z.,Zeng, Q.
Structure and assembly of the alpha-carboxysome in the marine cyanobacterium Prochlorococcus.
Nat.Plants, 10:661-672, 2024

PubMed Abstract: Carboxysomes are bacterial microcompartments that encapsulate the enzymes RuBisCO and carbonic anhydrase in a proteinaceous shell to enhance the efficiency of photosynthetic carbon fixation. The self-assembly principles of the intact carboxysome remain elusive. Here we purified α-carboxysomes from Prochlorococcus and examined their intact structures using single-particle cryo-electron microscopy to solve the basic principles of their shell construction and internal RuBisCO organization. The 4.2 Å icosahedral-like shell structure reveals 24 CsoS1 hexamers on each facet and one CsoS4A pentamer at each vertex. RuBisCOs are organized into three concentric layers within the shell, consisting of 72, 32 and up to 4 RuBisCOs at the outer, middle and inner layers, respectively. We uniquely show how full-length and shorter forms of the scaffolding protein CsoS2 bind to the inner surface of the shell via repetitive motifs in the middle and C-terminal regions. Combined with previous reports, we propose a concomitant 'outside-in' assembly principle of α-carboxysomes: the inner surface of the self-assembled shell is reinforced by the middle and C-terminal motifs of the scaffolding protein, while the free N-terminal motifs cluster to recruit RuBisCO in concentric, three-layered spherical arrangements. These new insights into the coordinated assembly of α-carboxysomes may guide the rational design and repurposing of carboxysome structures for improving plant photosynthetic efficiency.

PubMed: 38589484
DOI: 10.1038/s41477-024-01660-9

Experimental method

ELECTRON MICROSCOPY (4.2 Å)