The PRC-barrel is a partly opened all-beta barrel domain of approximately 80 residues long, which is found in several bacterial, archaeal and plant proteins.
The PRC-barrel domain is found in subunit H of the photosynthetic reaction centre (PRC) in purple bacteria. PRC is an integral membrane pigment-protein complex that carries out light-driven electron transfer reactions during photosynthesis. At the core of the reaction centre is a collection of light-harvesting cofactors and closely associated polypeptides. The core protein complex is made of L, M and H polypeptide subunits . The H subunit has a single transmembrane helix and a large cytoplasmic domain . The core of the cytoplasmic domain contains the PRC-barrel.
A PRC-barrel domain is also present at the C terminus of the pan-bacterial protein RimM, which is involved in ribosomal maturation and processing of 16S rRNA. A family of small proteins conserved in all known euryarchaea are composed entirely of a single stand-alone copy of the domain