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Publication Abstract from PubMed

Carboxysomes are capsid-like, CO2-fixing organelles that are present in all cyanobacteria and some chemoautotrophs and that substantially contribute to global primary production. They are composed of a selectively permeable protein shell that encapsulates Rubisco, the principal CO2-fixing enzyme, and carbonic anhydrase. As the centerpiece of the carbon-concentrating mechanism, by packaging enzymes that collectively enhance catalysis, the carboxysome shell enables the generation of a locally elevated concentration of substrate CO2 and the prevention of CO2 escape. A functional carboxysome consisting of an intact shell and cargo is essential for cyanobacterial growth under ambient CO2 concentrations. Using cryo-electron microscopy, we have determined the structure of a recombinantly produced simplified beta-carboxysome shell. The structure reveals the sidedness and the specific interactions between the carboxysome shell proteins. The model provides insight into the structural basis of selective permeability of the carboxysome shell and can be used to design modifications to investigate the mechanisms of cargo encapsulation and other physiochemical properties such as permeability. Notably, the permeability properties are of great interest for modeling and evaluating this carbon-concentrating mechanism in metabolic engineering. Moreover, we find striking similarity between the carboxysome shell and the structurally characterized, evolutionarily distant metabolosome shell, implying universal architectural principles for bacterial microcompartment shells.

Structure of a Synthetic beta-Carboxysome Shell.,Sutter M, Laughlin TG, Sloan NB, Serwas D, Davies KM, Kerfeld CA Plant Physiol. 2019 Nov;181(3):1050-1058. doi: 10.1104/pp.19.00885. Epub 2019 Sep, 9. PMID:31501298^[1]

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