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Publication Abstract from PubMed

Carboxysomes are anabolic bacterial microcompartments that play an essential role in CO2 fixation in cyanobacteria. This self-assembling proteinaceous organelle uses a polyhedral shell constructed by hundreds of shell protein paralogs to encapsulate the key CO2-fixing enzymes Rubisco and carbonic anhydrase. Deciphering the precise arrangement and structural organization of Rubisco enzymes within carboxysomes is crucial for understanding carboxysome formation and overall functionality. Here, we employed cryoelectron tomography and subtomogram averaging to delineate the 3D packaging of Rubiscos within beta-carboxysomes in the freshwater cyanobacterium Synechococcus elongatus PCC7942 grown under low light. Our results revealed that Rubiscos are arranged in multiple concentric layers parallel to the shell within the beta-carboxysome lumen. We also detected Rubisco binding with the scaffolding protein CcmM in beta-carboxysomes, which is instrumental for Rubisco encapsulation and beta-carboxysome assembly. Using Quantification conCATamer-based quantitative MS, we determined the absolute stoichiometric composition of the entire beta-carboxysome. This study provides insights into the assembly principles and structural variation of beta-carboxysomes, which will aid in the rational design and repurposing of carboxysome nanostructures for diverse bioengineering applications.

Rubisco packaging and stoichiometric composition of the native beta-carboxysome in Synechococcus elongatus PCC7942.,Sun Y, Sheng Y, Ni T, Ge X, Sarsby J, Brownridge PJ, Li K, Hardenbrook N, Dykes GF, Rockliffe N, Eyers CE, Zhang P, Liu LN Plant Physiol. 2024 Dec 24;197(1):kiae665. doi: 10.1093/plphys/kiae665. PMID:39680612^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.