tRNA pseudouridine synthase II, TruB (IPR014780)

Short name: tRNA_psdUridine_synth_TruB

Overlapping homologous superfamilies

Family relationships



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 [PMID: 10529181]:

  • Pseudouridine synthase I, TruA.
  • Pseudouridine synthase II, TruB, which contains and additional C-terminal PUA domain.
  • Pseudouridine synthase RsuA (ribosomal small subunit) and RluC/RluD (ribosomal large subunits), both of which contain an additional N-terminal alpha-L RNA-binding motif.
  • 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.

TruB is responsible for the pseudouridine residue present in the T loops of virtually all tRNAs. TruB recognises the preformed 3-D structure of the T loop primarily through shape complementarity. It accesses its substrate uridyl residue by flipping out the nucleotide and disrupts the tertiary structure of tRNA [PMID: 11779468].

This model is built on a seed alignment of bacterial proteins only. Saccharomyces cerevisiae protein YNL292w (Pus4) has been shown to be the pseudouridine 55 synthase of both cytosolic and mitochondrial compartments, active at no other position on tRNA and the only enzyme active at that position in the species. A distinct yeast protein YLR175w, (centromere/microtubule-binding protein CBF5) is an rRNA pseudouridine synthase, and the archaeal set is much more similar to CBF5 than to Pus4. It is unclear whether the archaeal proteins found by this model are tRNA pseudouridine 55 synthases like TruB, rRNA pseudouridine synthases like CBF5, or (as suggested by the absence of paralogs in the Archaea) both. CBF5 likely has additional, eukaryotic-specific functions.

GO terms

Biological Process

GO:0009451 RNA modification
GO:0001522 pseudouridine synthesis

Molecular Function

GO:0003723 RNA binding
GO:0009982 pseudouridine synthase activity

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.