This group consists of eukaryotic pseudouridine synthases similar to S. cerevisiae Pus3p. Pseudouridine synthases catalyze the isomerization of specific uridines in an RNA molecule to pseudouridines (5-ribosyluracil, psi) []. No cofactors are required. S. cerevisiae Pus3p makes psi38 and psi39 in tRNAs []. Mouse Pus3 has been shown to makes psi38 and, possibly also psi 39, in tRNAs []. Psi38 and psi39 are highly conserved in tRNAs from eubacteria, archea and eukarya [].
