Structural similarities in glutaminyl- and methionyl-tRNA synthetases suggest a common overall orientation of tRNA binding.
Detailed comparisons between the structures of the tRNA-bound Escherichia coli glutaminyl-tRNA (Gln-tRNA) synthetase [L-glutamine:tRNA(Gln) ligase (AMP-forming), EC 6.1.1.18] and recently refined E. coli methionyl-tRNA (Met-tRNA) synthetase [L-methionine:tRNA(Met) ligase (AMP-forming), EC 6.1.1.10] reveal significant similarities beyond the anticipated correspondence of their respective dinucleotide-fold domains. One similarity comprises a 23-amino acid alpha-helix-turn-beta-strand motif found in each enzyme within a domain that is inserted between the two halves of the dinucleotide binding fold. A second correspondence, which consists of two alpha-helices connected by a large loop and beta-strand, is located in the Gln-tRNA synthetase within a region that binds the inside corner of the "L"-shaped tRNA molecule. This structural motif contains a long alpha-helix, which extends along the entire length of the D and anticodon stems of the complexed tRNA. We suggest that the positioning of this helix relative to the dinucleotide fold plays a critical role in ensuring the proper global orientation of tRNA(Gln) on the surface of the enzyme. The structural correspondences suggest a similar overall orientation of binding of tRNA(Met) and tRNA(Gln) to their respective synthetases.
Perona
J J
JJ
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511.
Rould
M A
MA
Steitz
T A
TA
Risler
J L
JL
Zelwer
C
C
Brunie
S
S
D000604:Amino Acyl-tRNA Synthetases / Q000737:chemistry* / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology*; D008718:Methionine-tRNA Ligase / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D011487:Protein Conformation; D012351:RNA, Transfer, Gln / Q000737:chemistry* / Q000378:metabolism; D012358:RNA, Transfer, Met / Q000737:chemistry* / Q000378:metabolism
D012351:RNA, Transfer, Gln; D012358:RNA, Transfer, Met; D000604:Amino Acyl-tRNA Synthetases; D008718:Methionine-tRNA Ligase; C020659:glutaminyl-tRNA synthetase