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Lookup NU author(s): Dr Arnaud Basle, Dr Jon Marles-WrightORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
Carboxysomes in cyanobacteria and certain proteobacteria enable efficient CO2 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 CO2 and HCO3-, supplying elevated levels of CO2 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 Halothiobacillus neapolitanus (HnCsoSCA). HnCsoSCA adopts a trimer-of-dimers oligomeric structure without the incorporation of a zinc ion at its symmetric center. Using synthetic minishells, we demonstrate that HnCsoSCA interacts with the CsoS1A shell hexamer and is incorporated into the minishells at the inner surface, independent of the CsoS2 linker protein. HnCsoSCA truncations suggest nonspecific interactions between HnCsoSCA and CsoS1A. We further show that HnCsoSCA 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.
Author(s): Ng PC, Adegbite O, Li T, Basle A, Marles-Wright J, Liu L-N
Publication type: Article
Publication status: Published
Journal: Proceedings of the National Academy of Sciences of the United States of America
Year: 2025
Volume: 122
Issue: 46
Online publication date: 18/11/2025
Acceptance date: 13/10/2025
Date deposited: 25/11/2025
ISSN (electronic): 0024-8424
Publisher: National Academy of Sciences
URL: https://doi.org/10.1073/pnas.2523723122
DOI: 10.1073/pnas.2523723122
Data Access Statement: Cryo-EM density maps have been deposited in the Electron Microscopy Data Bank (EMDB) under accession codes EMD-51067 (HnCsoSCA) (80), EMD-51633 (minishell/CsoSCA?C) (81), and EMD-51641 (minishell/CsoSCA-C) (82). The corresponding atomic models have been deposited in the Protein Data Bank (PDB) under the accession codes 9G4T (HnCsoSCA) (83), 9GVC (minishell/CsoSCA?C) (84), and 9GW1 (minishell/ CsoSCA-C) (85)
PubMed id: 41223214
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