2. Editing Domain (“2 nd Sieve”) Catalytic Domain (“1 st Sieve”) Anticodon Binding Domain C-Terminal Coiled-Coil Domain 862 amino acids 25 α-helices 30 β-strands Overall Structure

3. Function Aminoacyl tRNA synthetases are enzymes that catalyze the esterification of a specific amino acid to a compatible cognate tRNA to form an aminoacyl- tRNA Class I vs. Class II: – 2’-OH, then 3’-OH – Directly to 3’-OH

4. “Double-Sieve” Concept

9. Aminoacylation Site Interactions Hydrophobic Pocket Pro 41 Pro 42 Asn 44 Ile 491 Trp 491 Trp 456 Asp 81

10. KMSKS Loop Met 529

11. Editing Domain Interactions Thr 214 Tyr 337 Phe 264 Leu 269 Leu 278 Glu 261 Glu 281

12. Editing Hydrophilic Pocket

13. Anticodon Binding Domain *nucleotides are in green, amino acids are in yellow

14. Kinetics for C-term. Domain o phosphates on A20 & A21 interact through salt bridges with Arg818 and Arg843 o G19 & C56 crucial of correct positioning of 3’ CCA end of tRNA into aminoacylation catalytic site

15. References 1.Fukai, S.; Nureki, O.; Sekine, S.; Shimada, A.; Tao, J.; Vassylyev, D.G.; Yokoyama, S. Structural Basis for Double-Sieve Discrimination of L-Valine from L-Isoleucine and L- Threonine by the Complex of tRNA Val and Valyl-tRNA Synthetase. Cell 2000, 103, 793-803. 2.Fukai, S.; Nureki, O.; Sekine, S.; Shimada, A.; Vassylyev, D.G.; Yogoyama, S. Mechanism of molecular interactions for tRNA Val recognition by valyl-tRNA synthetase. RNA 2003, 9, 100- 111. 3.Fukunaga, R.; Yokoyama, S. Structural Basis for Non-cognate Amino Acid Discrimination by the Valyl-tRNA Synthetase Editing Domain. J. Bio. Chem. 2005, 280 (33), 29937-29945. 4.Liu, M.; Chu, W.; Liu, J.C.H.; Horowitz, J. Role of acceptor stem conformation in tRNA Val recognition by its cognate synthetase. Nucleic Acids Res. 1997, 25, 4883-4890.