Structural Basis of RNA-Dependent Recruitment of Glutamine to the Genetic Code

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Science  30 Jun 2006:
Vol. 312, Issue 5782, pp. 1950-1954
DOI: 10.1126/science.1128470

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Glutaminyl–transfer RNA (Gln-tRNAGln) in archaea is synthesized in a pretranslational amidation of misacylated Glu-tRNAGln by the heterodimeric Glu-tRNAGln amidotransferase GatDE. Here we report the crystal structure of the Methanothermobacter thermautotrophicus GatDE complexed to tRNAGln at 3.15 angstroms resolution. Biochemical analysis of GatDE and of tRNAGln mutants characterized the catalytic centers for the enzyme's three reactions (glutaminase, kinase, and amidotransferase activity). A 40 angstrom–long channel for ammonia transport connects the active sites in GatD and GatE. tRNAGln recognition by indirect readout based on shape complementarity of the D loop suggests an early anticodon-independent RNA-based mechanism for adding glutamine to the genetic code.

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