Carboxysome

The carboxysome is a bacterial microcompartment, roughly 90-500 nm in diameter, made up of a protein shell, that contains enzymes involved in carbon fixation reactions. Carboxysomes are inclusion bodies that contain most, if not all, of the cell's ribulose 1,5-bisphosphate carboxylase,(carbon dioxide fixation enzyme), which is the rate limiting enzyme in the Calvin cycle. Carboxysomes are found in all cyanobacteria, some nitrifying bacteria, and thiobacilli. Carboxysomes are thought to be part of a wider group of protein micro-compartments that have dissimilar functions, but similar structures.