3h0r | pdb_00003h0r
Structure of trna-dependent amidotransferase gatcab from aquifex aeolicus
Structural highlights
FunctionGATA_AQUAE Allows the formation of correctly charged Gln-tRNA(Gln) through the transamidation of misacylated Glu-tRNA(Gln) in organisms which lack glutaminyl-tRNA synthetase. The reaction takes place in the presence of glutamine and ATP through an activated gamma-phospho-Glu-tRNA(Gln) (By similarity). Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedMany bacteria form Gln-tRNA(Gln) and Asn-tRNA(Asn) by conversion of the misacylated Glu-tRNA(Gln) and Asp-tRNA(Asn) species catalyzed by the GatCAB amidotransferase in the presence of ATP and an amide donor (glutamine or asparagine). Here, we report the crystal structures of GatCAB from the hyperthermophilic bacterium Aquifex aeolicus, complexed with glutamine, asparagine, aspartate, ADP, or ATP. In contrast to the Staphylococcus aureus GatCAB, the A. aeolicus enzyme formed acyl-enzyme intermediates with either glutamine or asparagine, in line with the equally facile use by the amidotransferase of these amino acids as amide donors in the transamidation reaction. A water-filled ammonia channel is open throughout the length of the A. aeolicus GatCAB from the GatA active site to the synthetase catalytic pocket in the B-subunit. A non-catalytic Zn(2+) site in the A. aeolicus GatB stabilizes subunit contacts and the ammonia channel. Judged from sequence conservation in the known GatCAB sequences, the Zn(2+) binding motif was likely present in the primordial GatB/E, but became lost in certain lineages (e.g., S. aureus GatB). Two divalent metal binding sites, one permanent and the other transient, are present in the catalytic pocket of the A. aeolicus GatB. The two sites enable GatCAB to first phosphorylate the misacylated tRNA substrate and then amidate the activated intermediate to form the cognate products, Gln-tRNA(Gln) or Asn-tRNA(Asn). Insights into tRNA-dependent amidotransferase evolution and catalysis from the structure of the Aquifex aeolicus enzyme.,Wu J, Bu W, Sheppard K, Kitabatake M, Kwon ST, Soll D, Smith JL J Mol Biol. 2009 Aug 28;391(4):703-16. Epub 2009 Jun 9. PMID:19520089[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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