InterPro domain: IPR042092

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 [ 1 , 2 ]:

• Pseudouridine synthase I, TruA.
• Pseudouridine synthase II, TruB, which contains and additional C-terminal PUA domain.
• Pseudouridine synthase RsuA. RluB, RluE and RluF are also part of this family.
• Pseudouridine synthase RluA. RluC and RluD belong to this family.
• Pseudouridine synthase TruD, which has a natural circular permutation in the catalytic domain, as well as an insertion of a family-specific alpha+beta subdomain.

This entry represents the C-terminal region of the catalytic domain found in pseudouridine synthases from the RsuA family, including: RsuA (acts on small ribosomal subunit), RluB, RluE and RluF (act on large ribosomal subunit) [ 3 ].

1. Role of cysteine residues in pseudouridine synthases of different families. Biochemistry 38, 13106-11
2. Enzymatic characterization and mutational studies of TruD--the fifth family of pseudouridine synthases. Arch. Biochem. Biophys. 489, 15-9
3. Domain organization and crystal structure of the catalytic domain of E.coli RluF, a pseudouridine synthase that acts on 23S rRNA. J. Mol. Biol. 359, 998-1009