title: Two distinct regions in Staphylococcus aureus GatCAB guarantee accurate tRNA recognition.
abstract: In many prokaryotes the biosynthesis of the amide aminoacyl-tRNAs, Gln-tRNA(Gln) and Asn-tRNA(Asn), proceeds by an indirect route in which mischarged Glu-tRNA(Gln) or Asp-tRNA(Asn) is amidated to the correct aminoacyl-tRNA catalyzed by a tRNA-dependent amidotransferase (AdT). Two types of AdTs exist: bacteria, archaea and organelles possess heterotrimeric GatCAB, while heterodimeric GatDE occurs exclusively in archaea. Bacterial GatCAB and GatDE recognize the first base pair of the acceptor stem and the D-loop of their tRNA substrates, while archaeal GatCAB recognizes the tertiary core of the tRNA, but not the first base pair. Here, we present the crystal structure of the full-length Staphylococcus aureus GatCAB. Its GatB tail domain possesses a conserved Lys rich motif that is situated close to the variable loop in a GatCAB:tRNA(Gln) docking model. This motif is also conserved in the tail domain of archaeal GatCAB, suggesting this basic region may recognize the tRNA variable loop to discriminate Asp-tRNA(Asn) from Asp-tRNA(Asp) in archaea. Furthermore, we identified a 3(10) turn in GatB that permits the bacterial GatCAB to distinguish a U1-A72 base pair from a G1-C72 pair; the absence of this element in archaeal GatCAB enables the latter enzyme to recognize aminoacyl-tRNAs with G1-C72 base pairs.
authors.affiliation: Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan.
authors.forename: Akiyoshi
authors.initials: A
authors.lastname: Nakamura
authors.forename: Kelly
authors.initials: K
authors.lastname: Sheppard
authors.forename: Junji
authors.initials: J
authors.lastname: Yamane
authors.forename: Min
authors.initials: M
authors.lastname: Yao
authors.forename: Dieter
authors.initials: D
authors.lastname: Söll
authors.forename: Isao
authors.initials: I
authors.lastname: Tanaka
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry*; D020029:Base Pairing; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019884:Nitrogenous Group Transferases / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D012343:RNA, Transfer / Q000737:chemistry*; D012348:RNA, Transfer, Asn / Q000737:chemistry; D012351:RNA, Transfer, Gln / Q000737:chemistry; D013211:Staphylococcus aureus / Q000201:enzymology*
chemical_list: D001426:Bacterial Proteins; D012348:RNA, Transfer, Asn; D012351:RNA, Transfer, Gln; D012343:RNA, Transfer; D019884:Nitrogenous Group Transferases