Involved in the formation of pseudouridine at the anticodon stem and loop of transfer-RNAs Pseudouridine is an isomer of uridine (5-(beta-D-ribofuranosyl) uracil, and id the most abundant modified nucleoside found in all cellular RNAs. The TruA-like proteins also exhibit a conserved sequence with a strictly conserved aspartic acid, likely involved in catalysis.
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]: