Deinococcus glutaminyl-tRNA synthetase is a chimer between proteins from an ancient and the modern pathways of aminoacyl-tRNA formation

• Published in: Nucleic acids research Vol. 35; no. 5; pp. 1421 - 1431
• Main Authors: Deniziak, Marzanna, Sauter, Claude, Becker, Hubert Dominique, Paulus, Caroline Alexandra, Giegé, Richard, Kern, Daniel
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01.03.2007; Oxford Publishing Limited (England)
• Subjects: Amino Acid Sequence; Amino Acyl-tRNA Synthetases - chemistry; Amino Acyl-tRNA Synthetases - genetics; Amino Acyl-tRNA Synthetases - metabolism; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Cellular Biology; Crystallography, X-Ray; Deinococcus - enzymology; Deinococcus radiodurans; Escherichia coli; Escherichia coli - enzymology; Evolution, Molecular; Gene Fusion; Kinetics; Life Sciences; Models, Molecular; Molecular Sequence Data; Nitrogenous Group Transferases - chemistry; Protein Structure, Tertiary; RNA, Transfer, Gln - chemistry; RNA, Transfer, Gln - metabolism; Sequence Alignment; Structural Biology
• ISSN: 0305-1048; 1362-4962
• DOI: 10.1093/nar/gkl1164

Glutaminyl-tRNA synthetase from Deinococcus radiodurans possesses a C-terminal extension of 215 residues appending the anticodon-binding domain. This domain constitutes a paralog of the Yqey protein present in various organisms and part of it is present in the C-terminal end of the GatB subunit of GatCAB, a partner of the indirect pathway of Gln-tRNAGln formation. To analyze the peculiarities of the structure-function relationship of this GlnRS related to the Yqey domain, a structure of the protein was solved from crystals diffracting at 2.3 Å and a docking model of the synthetase complexed to tRNAGln constructed. The comparison of the modeled complex with the structure of the E. coli complex reveals that all residues of E. coli GlnRS contacting tRNAGln are conserved in D. radiodurans GlnRS, leaving the functional role of the Yqey domain puzzling. Kinetic investigations and tRNA-binding experiments of full length and Yqey-truncated GlnRSs reveal that the Yqey domain is involved in tRNAGln recognition. They demonstrate that Yqey plays the role of an affinity-enhancer of GlnRS for tRNAGln acting only in cis. However, the presence of Yqey in free state in organisms lacking GlnRS, suggests that this domain may exert additional cellular functions.