Bacterial microcompartment containing the enzyme RuBisCo
Electron micrographs showing alpha-carboxysomes from the chemoautotrophic bacterium Halothiobacillus neapolitanus: (A) arranged within the cell, and (B) intact upon isolation. Scale bars indicate 100 nm.[1]
Carboxysomes are bacterial microcompartments (BMCs) consisting of polyhedral protein shells filled with the enzymes ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO)—the predominant enzyme in carbon fixation and the rate limiting enzyme in the Calvin cycle—and carbonic anhydrase.[2]
Carboxysomes are thought to have evolved as a consequence of the increase in oxygen concentration in the ancient atmosphere; this is because oxygen is a competing substrate to carbon dioxide in the RuBisCO reaction.[3] To overcome the inefficiency of RuBisCO, carboxysomes concentrate carbon dioxide inside the shell by means of co-localized carbonic anhydrase activity, which produces carbon dioxide from the bicarbonate that diffuses into the carboxysome. The resulting concentration of carbon dioxide near RuBisCO decreases the proportion of ribulose-1,5-bisphosphate oxygenation and thereby avoids costly photorespiratory reactions. The surrounding shell provides a barrier to carbon dioxide loss, helping to increase its concentration around RuBisCO.[4][5][6]
Carboxysomes are an essential part of the broader metabolic network called the Carbon dioxide-Concentrating Mechanism (CCM), which functions in two parts:[7] (1) Membrane transporters concentrate inorganic carbon (Ci) in the cell cytosol which is devoid of carbonic anhydrases. Carbon is primarily stored in the form of HCO3- which cannot re-cross the lipid membrane, as opposed to neutral CO2 which can easily escape the cell. This stockpiles carbon in the cell, creating a disequilibrium between the intracellular and extracellular environments of about 30x the Ci concentration in water.[8] (2) Cytosolic HCO3- diffuses into the carboxysome, where carboxysomal carbonic anhydrases dehydrate it back to CO2 in the vicinity of Rubisco, allowing Rubisco to operate at its maximal rate.
Carboxysomes are the best studied example of bacterial microcompartments, the term for functionally diverse organelles that are alike in having a protein shell.[9][10]
^Tsai Y, Sawaya MR, Cannon GC, Cai F, Williams EB, Heinhorst S, et al. (June 2007). "Structural analysis of CsoS1A and the protein shell of the Halothiobacillus neapolitanus carboxysome". PLOS Biology. 5 (6): e144. doi:10.1371/journal.pbio.0050144. PMC 1872035. PMID 17518518.
^Cite error: The named reference YeatesKerfeld2008 was invoked but never defined (see the help page).
^Cite error: The named reference Badger2003 was invoked but never defined (see the help page).
^Cite error: The named reference CaiMenon2009 was invoked but never defined (see the help page).
^Cite error: The named reference DouHeinhorst2008 was invoked but never defined (see the help page).
^Mangan NM, Flamholz A, Hood RD, Milo R, Savage DF (September 2016). "pH determines the energetic efficiency of the cyanobacterial CO2 concentrating mechanism". Proceedings of the National Academy of Sciences of the United States of America. 113 (36): E5354–E5362. Bibcode:2016PNAS..113E5354M. doi:10.1073/pnas.1525145113. PMC 5018799. PMID 27551079.
^Badger MR, Hanson D, Price GD (April 2002). "Evolution and diversity of CO2 concentrating mechanisms in cyanobacteria". Functional Plant Biology. 29 (3): 161–173. doi:10.1071/PP01213. PMID 32689463.
^Price GD (September 2011). "Inorganic carbon transporters of the cyanobacterial CO2 concentrating mechanism". Photosynthesis Research. 109 (1–3): 47–57. doi:10.1007/s11120-010-9608-y. PMID 21359551. S2CID 25867128.
^Cite error: The named reference KerfeldErbilgin2015 was invoked but never defined (see the help page).
^Cite error: The named reference AxenErbilgin2014 was invoked but never defined (see the help page).
Carboxysomes are bacterial microcompartments (BMCs) consisting of polyhedral protein shells filled with the enzymes ribulose-1,5-bisphosphate carboxylase/oxygenase...
in metabolic pathways, and protein complexes such as proteasomes and carboxysomes that enclose and separate parts of the cytosol. The term "cytosol" was...
revealed that at least some prokaryotes have microcompartments, such as carboxysomes. These subcellular compartments are 100–200 nm in diameter and are enclosed...
to carboxysomes. The term metabolosome is used to refer to such catabolic BMCs (in contrast to the autotrophic carboxysome). Although the carboxysome, propanediol...
number of pentagons and hexagons. Protein enclosing bacterial organelles carboxysome is also made up of pentameric protein. Synthetic pentameric proteins...
the widespread prevalence of the bacterial microcompartments known as carboxysomes, which co-operate with active transporters of CO2 and bicarbonate, in...
the carboxysome, releases CO2 from dissolved hydrocarbonate ions (HCO− 3). Before the CO2 can diffuse out, RuBisCO concentrated within the carboxysome quickly...
in a few chemolithotrophs and marine cyanobacteria that contain cso-carboxysomes. Recent 3-dimensional analyses suggest that ζ-CA bears some structural...
which compartmentalise aspects of bacterial metabolism, such as the carboxysome. Additionally, bacteria have a multi-component cytoskeleton to control...
carbohydrate-enclosed microcompartments, which have distinct physiological roles (e.g. carboxysomes or gas vacuoles). Most prokaryotes are between 1 μm and 10 μm, but they...
compartmentalization is not found in prokaryotic cells., but the discovery of carboxysomes and many other metabolosomes revealed that prokaryotic cells are capable...
the plasma membrane in light yellow, the thylakoid membrane in green, carboxysomes in cyan, the polyphosphate body in blue, adsorbed phages on the sides...
chloroplasts also contain concentric unstacked thylakoids, which surround a carboxysome – an icosahedral structure that glaucophyte chloroplasts and cyanobacteria...
inclusions, glycogen granules, and more importantly, highly structured carboxysomes. Cells are known to be motile by a gliding method and a novel uncharacterized...
a function performed by the membrane-bound organelles in eukaryotes. Carboxysomes are bacterial microcompartments found in many autotrophic bacteria such...
bacteria. These shell proteins form the polyhedral structure of the carboxysome and related structures that plays a metabolic role in bacteria. The BMC...
(i.e. changing C3 plants into C4 plants), by placing the rubisco in a carboxysome, by adding CO2 pumps in the cell wall, or by changing the leaf form or...
(RuBisCO). Pyrenoids therefore seem to have a role analogous to that of carboxysomes in cyanobacteria. Algae are restricted to aqueous environments, even...
structural differences. Instead of the pyrenoid, cyanobacteria contain carboxysomes, which have a protein shell, and linker proteins packing RuBisCO inside...
examples of enzyme encapsulation in protein-based cage structures (Example: Carboxysomes, Ferritin and Encapsulin), Cytochrome C was encapsulated in a 9 nm small...
protein shell that encloses the bacterial micro-compartments known as carboxysomes. In immunology, an MHC pentamer is a reagent used to detect antigen-specific...
Cells in the genus Nitrobacter reproduce by budding or binary fission. Carboxysomes, which aid carbon fixation, are found in lithoautotrophically and mixotrophically...
during denitrification. The autotrophic members of the class do not use carboxysomes to concentrate carbon dioxide or improve RuBisCO efficiency as a carboxylase...
common model organism for autotrophy research, in particular study of carboxysomes and their role in carbon concentration and maintaining RuBisCO efficiency...
lethal cyanotoxins. Synechococcus, a widespread marine cyanobacterium Carboxysomes appearing as polyhedral dark structures within a species of Synechococcus...
concentrations. In cyanobacteria, concentrations of CO2 are increased using a carboxysome, an icosahedral protein compartment about 100 nm in diameter that selectively...
therapies for use in both humans and animals. Silver has characterized the carboxysome – the major carbon-fixing structure in cyanobacteria – to enhance photosynthetic...
thylakoid membrane layers forming evenly spaced concentric rings and its carboxysomes and polyphosphate bodies are located in the central cytoplasmic region...
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