Evolution of eukaryal tRNA-guanine transglycosylase: insight gained from the heterocyclic substrate recognition by the wild-type and mutant human and Escherichia coli tRNA-guanine transglycosylases

Abstract

The enzyme tRNA-guanine transglycosylase (TGT) is involved in the queuosine modification of tRNAs in eukarya and eubacteria and in the archaeosine modification of tRNAs in archaea. However, the different classes of TGTs utilize different heterocyclic substrates (and tRNA in the case of archaea). Based on the X-ray structural analyses, an earlier study [Stengl et al. (2005) Mechanism and substrate specificity of tRNA-guanine transglycosylases (TGTs): tRNA-modifying enzymes from the three different kingdoms of life share a common catalytic mechanism. Chembiochem, 6, 1926–1939] has made a compelling case for the divergent evolution of the eubacterial and archaeal TGTs. The X-ray structure of the eukaryal class of TGTs is not known. We performed sequence homology and phylogenetic analyses, and carried out enzyme kinetics studies with the wild-type and mutant TGTs from Escherichia coli and human using various heterocyclic substrates that we synthesized. Observations with the Cys145Val (E. coli) and the corresponding Val161Cys (human) TGTs are consistent with the idea that the Cys145 evolved in eubacterial TGTs to recognize preQ1 but not queuine, whereas the eukaryal equivalent, Val161, evolved for increased recognition of queuine and a concomitantly decreased recognition of preQ1. Both the phylogenetic and kinetic analyses support the conclusion that all TGTs have divergently evolved to specifically recognize their cognate heterocyclic substrates.

Plant, Animal, and Fungal Micronutrient Queuosine Is Salvaged by Members of the DUF2419 Protein Family

“…The known and published sequences of the characterized bacterial TGT ( E. coli TGT, AAA24667 68 ), and human QTRT1, and QTRTD1 (IPI00215974.2 and IPI00783033.2, respectively 17 ) were used as entry points for all database queries. The BLAST tools 69 and resources at NCBI (National Center for Biotechnology Information, ) were routinely used.…”

Biosynthesis of pyrrolopyrimidines

“…Complex formation, either by co-expression [84] or in vitro mixing [85] leads to active protein. The bacterial and mammalian proteins have been proposed to have evolved via divergent evolution, and there is evidence that small changes in active site architecture are responsible for their differential substrate recognition properties [86,87]. …”

Protein universe containing a PUA RNA‐binding domain

“…These proteins are only present in archaea [9] and are distantly related to the family of queuine-specific TGTs [35,41] and to the proteins that contain the phosphoadenosine phosphosulfate reductase domain [42] of bacteria and eukaryotes, which lack the PUA domain.…”

“…May be specifically responsible for archaeosine incorporation at different sites in tRNA molecules [41] Only in: P. furiosus, P. abyssi and M. jannaschii…”