Structural basis for anticodon recognition by discriminating glutamyl-tRNA synthetase.
Glutamyl-tRNA synthetases (GluRSs) are divided into two distinct types, with regard to the presence or absence of glutaminyl-tRNA synthetase (GlnRS) in the genetic translation systems. In the original 19-synthetase systems lacking GlnRS, the 'non-discriminating' GluRS glutamylates both tRNAGlu and tRNAGln. In contrast, in the evolved 20-synthetase systems with GlnRS, the 'discriminating' GluRS aminoacylates only tRNAGlu. Here we report the 2.4 A resolution crystal structure of a 'discriminating' GluRS.tRNAGlu complex from Thermus thermophilus. The GluRS recognizes the tRNAGlu anticodon bases via two alpha-helical domains, maintaining the base stacking. We show that the discrimination between the Glu and Gln anticodons (34YUC36 and 34YUG36, respectively) is achieved by a single arginine residue (Arg 358). The mutation of Arg 358 to Gln resulted in a GluRS that does not discriminate between the Glu and Gln anticodons. This change mimics the reverse course of GluRS evolution from anticodon 'non-dicsriminating' to 'discriminating'.
Cellular Signaling Laboratory, RIKEN Harima Institute at SPring-8, 1-1-1 Kouto, Mikazuki-cho, Sayo, Hyogo 679-5148, Japan.
S
S
Sekine
O
O
Nureki
A
A
Shimada
D G
DG
Vassylyev
S
S
Yokoyama
D000926:Anticodon / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D018360:Crystallography, X-Ray; D019143:Evolution, Molecular; D005975:Glutamate-tRNA Ligase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism; D005973:Glutamine / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D017354:Point Mutation / Q000235:genetics; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012352:RNA, Transfer, Glu / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D016963:Thermus thermophilus / Q000201:enzymology* / Q000235:genetics*
D000926:Anticodon; D012352:RNA, Transfer, Glu; D005973:Glutamine; D018698:Glutamic Acid; D005975:Glutamate-tRNA Ligase