Inhibition by L-aspartol adenylate of a nondiscriminating aspartyl-tRNA synthetase reveals differences between the interactions of its active site with tRNA(Asp) and tRNA(Asn).
Asparaginyl-tRNA formation in Pseudomonas aeruginosa PAO1 involves a nondiscriminating aspartyl-tRNA synthetase (ND-AspRS) which forms Asp-tRNA(Asp) and Asp-tRNA(Asn), and a tRNA-dependent amidotransferase which transamidates the latter into Asn-tRNA(Asn). We report here that the inhibition of this ND-AspRS by L-aspartol adenylate (Asp-ol-AMP), a stable analog of the natural reaction intermediate L-aspartyl adenylate, is biphasic because the aspartylation of the two tRNA substrates of ND-AspRS, tRNA(Asp) and tRNA(Asn), are inhibited with different Ki values (41 microM and 215 microM, respectively). These results reveal that the two tRNA substrates of ND-AspRS interact differently with its active site. Yeast tRNA(Asp) transcripts with some identity elements replaced by those of tRNA(Asn) have their aspartylation inhibited with Ki values different from that for the wild-type transcript. Therefore, aminoacyl adenylate analogs, which are competitive inhibitors of their cognate aminoacyl-tRNA synthetase, can be used to probe rapidly the role of various structural elements in positioning the tRNA acceptor end in the active site.
Bernard
Dominic
D
Centre de Recherche en Infectiologie, CHUL, 2705 Boul. Laurier RC-709, Québec, QC, Canada.
Akochy
Pierre-Marie
PM
Bernier
Stéphane
S
Fisette
Olivier
O
Brousseau
Olivier Côté
OC
Chênevert
Robert
R
Roy
Paul H
PH
Lapointe
Jacques
J
D000249:Adenosine Monophosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D001226:Aspartate-tRNA Ligase / Q000037:antagonists & inhibitors*; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D001483:Base Sequence; D001665:Binding Sites; D017931:DNA Primers; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D009690:Nucleic Acid Conformation; D012348:RNA, Transfer, Asn / Q000737:chemistry / Q000378:metabolism*; D012349:RNA, Transfer, Asp / Q000737:chemistry / Q000378:metabolism*
D017931:DNA Primers; D004791:Enzyme Inhibitors; D012348:RNA, Transfer, Asn; D012349:RNA, Transfer, Asp; C052755:aspartyl adenylate; D001224:Aspartic Acid; D000249:Adenosine Monophosphate; D001226:Aspartate-tRNA Ligase