Members of this family are involved in modifying bases in RNA molecules. They carry out the conversion of uracil bases to pseudouridine. This family includes TruB, a pseudouridylate synthase that specifically converts uracil 55 to pseudouridine in most tRNAs. This family also includes Cbf5p that modifies rRNA .
Pseudouridine synthases catalyse the isomerisation of uridine to pseudouridine (Psi) in a variety of RNA molecules, and may function as RNA chaperones. Pseudouridine is the most abundant modified nucleotide found in all cellular RNAs. There are four distinct families of pseudouridine synthases that share no global sequence similarity, but which do share the same fold of their catalytic domain(s) and uracil-binding site and are descended from a common molecular ancestor. The catalytic domain consists of two subdomains, each of which has an alpha+beta structure that has some similarity to the ferredoxin-like fold (note: some pseudouridine synthases contain additional domains). The active site is the most conserved structural region of the superfamily and is located between the two homologous domains. These families are [PUBMED:10529181]:
Lafontaine DLJ, Bousquet-Antonelli C, Henry Y, Caizergues-Ferrer M, Tollervey D; , Genes Dev 1998;12:527-537.: The box H + ACA snoRNAs carry Cbf5p, the putative rRNA pseudouridine synthase. PUBMED:9472021 EPMC:9472021.