The PRC-barrel: a widespread, conserved domain shared by photosynthetic reaction center subunits and proteins of RNA metabolism
National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
Genome Biology 2002, 3:research0061-research0061.9 doi:10.1186/gb-2002-3-11-research0061Published: 14 October 2002
The H subunit of the purple bacterial photosynthetic reaction center (PRC-H) is important for the assembly of the photosynthetic reaction center and appears to regulate electron transfer during the reduction of the secondary quinone. It contains a distinct cytoplasmic β-barrel domain whose fold has no close structural relationship to any other well known β-barrel domain.
We show that the PRC-H β-barrel domain is the prototype of a novel superfamily of protein domains, the PRC-barrels, approximately 80 residues long, which is 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. Versions of this domain from photosynthetic proteobacteria contain a conserved acidic residue that is thought to regulate the reduction of quinones in the light-induced electron-transfer reaction. Closely related forms containing this acidic residue are also found in several non-photosynthetic bacteria, as well as in cyanobacteria, which have reaction centers with a different organization. We also show that the domain contains several determinants that could mediate specific protein-protein interactions.
The PRC-barrel is a widespread, ancient domain that appears to have been recruited to a variety of biological systems, ranging from RNA processing to photosynthesis. Identification of this versatile domain in numerous proteins could aid investigation of unexplored aspects of their biology.