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A Molecular Tunnel Required for Cooperation of an Asparaginase and a Glu‐tRNA Gln Kinase in Gln‐tRNA Formation
Author(s) -
Sheppard Kelly,
Feng Liang,
Oshikane Hiroyuki,
Nakamura Yuko,
Fukai Shuya,
Nureki Osamu,
Söll Dieter
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a503-a
Subject(s) - transfer rna , enzyme , amide , glutamine amidotransferase , glutaminase , chemistry , biochemistry , atp hydrolysis , archaea , gene , stereochemistry , amino acid , rna , atpase , glutamine
Most prokaryotes form Gln‐tRNA Gln by transformation of Glu‐tRNA Gln in the presence of ATP and an amide donor. Archaea contain a unique tRNA‐dependent heterodimeric enzyme, GatDE, for this purpose. Our studies with the Methanothermobacter thermautotrophicus enzyme show that GatD acts as a glutaminase to liberate ammonia from the amide donors Gln or Asn. Its activity is strongly activated by the presence of GatE, Glu‐tRNA Gln and ATP implying a tight coupling of amide donor hydrolysis and transamidation. GatD catalyzes the reaction in a manner similar to L‐asparaginases as predicted by sequence similarity and shown in the M. thermautotrophicus GatDE:tRNA Gln co‐crystal structure. GatE is a kinase that forms γ‐phosphoryl‐Glu‐tRNA Gln , the activated intermediate, required for the subsequent transamidation. The crystal structure reveals a molecular tunnel between the active sites of both subunits to channel ammonia from GatD to GatE where amidation takes place to form Gln‐tRNA Gln . Enzymatic analysis of mutant GatDE enzymes is in agreement with the predictions of the crystal structure. These data provide mechanistic and structural insights into the evolutionary link between metabolism and translation. This work was supported by grants from NIGMS, National Institutes of Health, and the U. S. Department of Energy.