Responsible for synthesis of pseudouridine from uracil-55 in the psi GC loop of transfer RNAs (PubMed:9358157). Also catalyzes pseudouridylation of mRNAs with the consensus sequence 5'-GGUUCRA-3' (PubMed:25219674). uridine(55) in tRNA = pseudouridine(55) in tRNA a uridine in mRNA = a pseudouridine in mRNA Present with 3990 molecules/cell in log phase SD medium. Belongs to the pseudouridine synthase TruB family.