Structural basis for tRNA-dependent amidotransferase function.
Besides direct charging of tRNAs by aminoacyl-tRNA synthetases, indirect routes also ensure attachment of some amino acids onto tRNA. Such routes may explain how new amino acids entered into protein synthesis. In archaea and in most bacteria, tRNA(Gln) is first misaminoacylated by glutamyl-tRNA synthetase. Glu-tRNA(Gln) is then matured into Gln-tRNA(Gln) by a tRNA-dependent amidotransferase. We report the structure of a tRNA-dependent amidotransferase-that of GatDE from Pyrococcus abyssi. The 3.0 A resolution crystal structure shows a tetramer with two GatD molecules as the core and two GatE molecules at the periphery. The fold of GatE cannot be related to that of any tRNA binding enzyme. The ammonium donor site on GatD and the tRNA site on GatE are markedly distant. Comparison of GatD and L-asparaginase structures shows how the motion of a beta hairpin region containing a crucial catalytic threonine may control the overall reaction cycle of GatDE.
Schmitt
Emmanuelle
E
Laboratoire de Biochimie, Unité Mixte de Recherche 7654, CNRS-Ecole Polytechnique, F-91128 Palaiseau cedex, France. emma@botrytis.polytechnique.fr
Panvert
Michel
M
Blanquet
Sylvain
S
Mechulam
Yves
Y
D000595:Amino Acid Sequence; D000604:Amino Acyl-tRNA Synthetases / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D019281:Dimerization; D005975:Glutamate-tRNA Ligase / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019884:Nitrogenous Group Transferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D014176:Protein Biosynthesis; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry; D043903:Pyrococcus abyssi / Q000201:enzymology; D019642:RNA, Archaeal / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D012329:RNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012343:RNA, Transfer / Q000737:chemistry* / Q000378:metabolism*; D012351:RNA, Transfer, Gln / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013912:Threonine / Q000737:chemistry; D014961:X-Ray Diffraction
D021122:Protein Subunits; D019642:RNA, Archaeal; D012329:RNA, Bacterial; D012351:RNA, Transfer, Gln; D013912:Threonine; D012343:RNA, Transfer; D019884:Nitrogenous Group Transferases; D000604:Amino Acyl-tRNA Synthetases; D005975:Glutamate-tRNA Ligase