The PRC-barrel is an all beta barrel domain found in photosystem reaction centre subunit H of the purple bacteria and RNA metabolism proteins of the RimM group. PRC-barrels are approximately 80 residues long, and found widely represented in bacteria, archaea and plants. This domain is also present at the carboxyl 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 [1].

1: The PRC-barrel: a widespread, conserved domain shared by photosynthetic reaction center subunits and proteins of RNA metabolism. Anantharaman V, Aravind L; Genome Biol 2002;3:RESEARCH0061. PMID:12429060

2: Refined crystal structures of reaction centres from Rhodopseudomonas viridis in complexes with the herbicide atrazine and two chiral atrazine derivatives also lead to a new model of the bound carotenoid. Lancaster CR, Michel H; J Mol Biol 1999;286:883-898. PMID:10024457