The carAB operon in E. coli contains two genes which produce the alpha and beta, or small and large chains of the carbamoyl-phosphate synthase protein. This protein is involved in the L-arginine biosynthesis pathway, and because of this, it can be repressed by the arginine repressor protein. This repressor is preesent when arginine is, preventing the biosynthesis of excess arginine. The first gene in this operon, carA, encodes the alpha or small chain of carbamoyl-phosphate synthase. The second gene, carB, encodes the beta or large chain of the same protein. One of each subunit combines in a heterodimer, which then interact with three other heterodomers to form the final carbamoyl-phosphate synthase protein. This protein is used in the formation of carbamoyl phosphate from glutamine, hydrogen carbonate, ATP and water. This reaction is part of the L-arginine biosynthesis pathway.

Operon: Carbamoyl Phosphate Synthetase References