9GVC

Cryo-EM structure of Halothiobacillus neapolitanus alpha-carboxysome T=4 mini-shell containing CTD truncated mutant of CsoSCA

Summary for 9GVC

• Entry DOI: 10.2210/pdb9gvc/pdb
• EMDB information: 51633
• Descriptor: Carboxysome shell vertex protein CsoS4A, Major carboxysome shell protein CsoS1A (3 entities in total)
• Functional Keywords: carboxysome, carbonic anhydrase, structural protein
• Biological source: Halothiobacillus neapolitanus; More
• Total number of polymer chains: 4
• Total formula weight: 38820.72

Authors

Ng, P.C.,Basle, A.,Liu, L.N.,Marles-Wright, J. (deposition date: 2024-09-23, release date: 2025-10-08, Last modification date: 2025-11-26)

Primary citation

Ng, P.C.,Adegbite, O.,Li, T.,Basle, A.,Marles-Wright, J.,Liu, L.N.
Structure and encapsulation of carbonic anhydrase within the alpha-carboxysome.
Proc.Natl.Acad.Sci.USA, 122:e2523723122-e2523723122, 2025

PubMed Abstract: Carboxysomes in cyanobacteria and certain proteobacteria enable efficient CO fixation by encapsulating ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and carbonic anhydrase (CA) within a semipermeable shell. Sequestered CA catalyze the rapid interconversion of CO and HCO, supplying elevated levels of CO to boost Rubisco carboxylation. Despite its essential role, the structure and encapsulation of CA within carboxysomes remain poorly understood. Here, we determined the molecular structure of α-carboxysomal CA from the model chemoautotrophic bacterium (CsoSCA). CsoSCA adopts a trimer-of-dimers oligomeric structure without the incorporation of a zinc ion at its symmetric center. Using synthetic minishells, we demonstrate that CsoSCA interacts with the CsoS1A shell hexamer and is incorporated into the minishells at the inner surface, independent of the CsoS2 linker protein. CsoSCA truncations suggest nonspecific interactions between CsoSCA and CsoS1A. We further show that CsoSCA bridges Rubisco and the shell facets. Our study offers insights into the assembly and encapsulation mechanisms of α-carboxysomes and provides the framework for reprogramming carboxysome structures for synthetic biology and biotechnological applications.

PubMed: 41223214
DOI: 10.1073/pnas.2523723122

Experimental method

ELECTRON MICROSCOPY (1.82 Å)