title: YrdC exhibits properties expected of a subunit for a tRNA threonylcarbamoyl transferase.
abstract: The post-transcriptional nucleoside modifications of tRNA's anticodon domain form the loop structure and dynamics required for effective and accurate recognition of synonymous codons. The N(6)-threonylcarbamoyladenosine modification at position 37 (t(6)A(37)), 3'-adjacent to the anticodon, of many tRNA species in all organisms ensures the accurate recognition of ANN codons by increasing codon affinity, enhancing ribosome binding, and maintaining the reading frame. However, biosynthesis of this complex modification is only partially understood. The synthesis requires ATP, free threonine, a single carbon source for the carbamoyl, and an enzyme yet to be identified. Recently, the universal protein family Sua5/YciO/YrdC was associated with t(6)A(37) biosynthesis. To further investigate the role of YrdC in t(6)A(37) biosynthesis, the interaction of the Escherichia coli YrdC with a heptadecamer anticodon stem and loop of lysine tRNA (ASL(Lys)(UUU)) was examined. YrdC bound the unmodified ASL(Lys)(UUU) with high affinity compared with the t(6)A(37)-modified ASL(Lys)(UUU) (K(d) = 0.27 ± 0.20 μM and 1.36 ± 0.39 μM, respectively). YrdC also demonstrated specificity toward the unmodified versus modified anticodon pentamer UUUUA and toward threonine and ATP. The protein did not significantly alter the ASL architecture, nor was it able to base flip A(37), as determined by NMR, circular dichroism, and fluorescence of 2-aminopuine at position 37. Thus, current data support the hypothesis that YrdC, with many of the properties of a putative threonylcarbamoyl transferase, most likely functions as a component of a heteromultimeric protein complex for t(6)A(37) biosynthesis.
authors.affiliation: Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina 27695-7622, USA.
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: Harris
authors.forename: Victoria
authors.initials: V
authors.lastname: Jones
authors.forename: Yann
authors.initials: Y
authors.lastname: Bilbille
authors.forename: Manal A
authors.initials: MA
authors.lastname: Swairjo
authors.forename: Paul F
authors.initials: PF
authors.lastname: Agris
mesh_terms: D015075:2-Aminopurine / Q000737:chemistry / Q000378:metabolism; D000241:Adenosine / Q000031:analogs & derivatives / Q000737:chemistry / Q000235:genetics; D000255:Adenosine Triphosphate / Q000378:metabolism; D000926:Anticodon; D020029:Base Pairing; D002942:Circular Dichroism / Q000379:methods; D003062:Codon; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics*; D005453:Fluorescence; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D012323:RNA Processing, Post-Transcriptional; D012329:RNA, Bacterial / Q000235:genetics; D012343:RNA, Transfer / Q000235:genetics*; D016601:RNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics*; D012269:Ribosomal Proteins / Q000737:chemistry / Q000235:genetics; D013912:Threonine / Q000235:genetics / Q000378:metabolism
chemical_list: D000926:Anticodon; D003062:Codon; D029968:Escherichia coli Proteins; C111429:N6-methyl-N6-threonylcarbamoyladenosine; D012329:RNA, Bacterial; D016601:RNA-Binding Proteins; C092748:RbfA protein, E coli; D012269:Ribosomal Proteins; C426646:YrdC protein, E coli; D013912:Threonine; D015075:2-Aminopurine; D000255:Adenosine Triphosphate; D012343:RNA, Transfer; D000241:Adenosine