This group is comprised of eukaryotic, bacterial and archeal proteins similar to eight site specific Escherichia coli pseudouridine synthases: RsuA, RluA, RluB, RluC, RluD, RluE, RluF and TruA. Pseudouridine synthases catalyze the isomerization of specific uridines in a n RNA molecule to pseudouridines (5-ribosyluracil, psi) requiring no cofactors. E. coli RluC for example makes psi955, 2504 and 2580 in 23S RNA. Some psi sites such as psi1917 in 23S RNA made by RluD are universally conserved. Other psi sites occur in a more restricted fashion, for example psi2819 in 21S mitochondrial ribosomal RNA made by S. cerevisiae Pus5p is only found in mitochondrial large subunit rRNAs from some other species and in gram negative bacteria. The E. coli counterpart of this psi residue is psi2580 in 23S rRNA. psi2604in 23S RNA made by RluF has only been detected in E.coli.
Jiyao W et al.(2023). "The conserved domain database in 2023.",