THE CRYSTAL-STRUCTURES OF THERMUS-THERMOPHILUS LYSYL-TRANSFER-RNA SYNTHETASE COMPLEXED WITH ESCHERICHIA-COLI TRNA(LYS) AND A THERMUS-THERMOPHILUS TRNA(LYS) TRANSCRIPT - ANTICODON RECOGNITION AND CONFORMATIONAL-CHANGES UPON BINDING OF A LYSYL-ADENYLATE ANALOG

The crystal structures of Thermus thermophilus lysyl-tRNA synthetase, a class IIb aminoacyl-tRNA synthetase, complexed with Escherichia coli tRNA(Lys)(mnm(5) s(2)UUU) at 2.75 Angstrom resolution and with a T.th ermophilus tRNA(Lys)(CUU) transcript at 2.9 Angstrom resolution are de scribed. In both complexes only the tRNA anticodon stem-loop is well o rdered. The mode of binding of the anticodon stem-loop to the N-termin al beta-barrel domain is similar to that previously found for the homo logous class IIb aspartyl-tRNA synthetase-tRNA(Asp) complex except in the region of the wobble base 34 where either mnm(5)s(2)U or C can be accommodated. The specific recognition of the other anticodon bases, U -35 and U-36, which are both major identity elements in the lysine sys tem, is also described. Additional crystallographic data on a ternary complex with a lysyl-adenylate analogue show that binding of the inter mediate induces significant conformational changes in the vicinity of the active site of the enzyme.