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Nanocompartment
Bacterial microcompartments (BMCs) are organelle-like structures found in bacteria. They consist of a protein shell that encloses enzymes and other proteins. BMCs are typically about 40–200 nanometers in diameter and are made entirely of proteins. The shell functions like a membrane, as it is selectively permeable. Other protein-based compartments found in bacteria and archaea include encapsulin nanocompartments and gas vesicles. Discovery The first BMCs were observed in the 1950s in electron micrographs of cyanobacteria, and were later named carboxysomes after their role in carbon fixation was established. Until the 1990s, carboxysomes were thought to be an oddity confined to certain autotrophic bacteria. But then genes coding for proteins homologous to those of the carboxysome shell were identified in the ''pdu'' (propanediol utilization) and ''eut'' (ethanolamine utilization) operons. Subsequently, transmission electron micrographs of ''Salmonella'' cells grown on propanedi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Encapsulin Nanocompartment
Encapsulin nanocompartments, or encapsulin protein cages, are spherical bacterial organelle-like compartments roughly 25-30 nm in diameter that are involved in various aspects of metabolism, in particular protecting bacteria from oxidative stress. Encapsulin nanocompartments are structurally similar to the HK97 bacteriophage and their function depends on the proteins loaded into the nanocompartment. The sphere is formed from 60 (for a 25 nm sphere) or 180 (for a 30 nm sphere) copies of a single protomer, termed encapsulin. Their structure has been studied in great detail using X-ray crystallography and cryo-electron microscopy. A number of different types of proteins have been identified as being loaded into encapsulin nanocompartments. Peroxidases or proteins similar to ferritin Ferritin is a universal intracellular protein that stores iron and releases it in a controlled fashion. The protein is produced by almost all living organisms, including archaea, bact ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gas Vesicle
Gas vesicles, also known as gas vacuoles, are nanocompartments in certain prokaryotic organisms, which help in buoyancy. Gas vesicles are composed entirely of protein; no lipids or carbohydrates have been detected. Function Gas vesicles occur primarily in aquatic organisms as they are used to modulate the cell's buoyancy and modify the cell's position in the water column so it can be optimally located for photosynthesis or move to locations with more or less oxygen. Organisms that could float to the air–liquid interface out competes other aerobes that cannot rise in a water column, through using up oxygen in the top layer. In addition, gas vesicles can be used to maintain optimum salinity by positioning the organism in specific locations in a stratified body of water to prevent osmotic shock. High concentrations of solute will cause water to be drawn out of the cell by osmosis, causing cell lysis. The ability to synthesize gas vesicles is one of many strategies that allow h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Encapsulin
The encapsulins are a family of bacterial proteins that serve as the main structural components of encapsulin nanocompartments. There are several different encapsulin proteins, including EncA, which forms the shell, and EncB, EncC, and EncD, which form the core. References {{reflist Cell biology Metabolism Biological engineering Bacterial proteins ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carboxysome And Bacterial Microcompartments
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-determining step, rate limiting enzyme in the Calvin cycle—and carbonic anhydrase. 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. 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 Photorespiration, photorespiratory reactions. The surrounding she ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
