Tyr-426 of the Escherichia coli asparaginyl-tRNA synthetase, an amino acid in a C-terminal conserved motif, is involved in ATP binding.
Sequence comparisons of the E. coli asparaginyl-tRNA synthetase (NRSEC) with aminocyl-tRNA synthetase sequences of class II enzymes show significant homologies with aspartyl- and lysyl-tRNA synthetases. Three conserved regions were found, one of which is located in the C-terminal part of the NRSEC sequence. Site-directed mutagenesis was performed in this conserved region. A single point mutation Tyr-426----Ser results in a 15-fold increase in the Km for ATP, while all the other kinetic parameters remain unchanged. The replacement of this Tyr-426 by a Phe does not affect the kinetic behaviour of the enzyme. These data indicate that Tyr-426 is part of the ATP binding site.
Anselme
J
J
European Molecular Biology Laboratory, Grenoble, France.
Härtlein
M
M
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000595:Amino Acid Sequence; D000604:Amino Acyl-tRNA Synthetases / Q000235:genetics* / Q000378:metabolism; D001226:Aspartate-tRNA Ligase; D001483:Base Sequence; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D005798:Genes, Bacterial; D007700:Kinetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D012346:RNA, Transfer, Amino Acyl; D012689:Sequence Homology, Nucleic Acid; D013379:Substrate Specificity; D014443:Tyrosine / Q000737:chemistry / Q000378:metabolism*
D012346:RNA, Transfer, Amino Acyl; D014443:Tyrosine; D000255:Adenosine Triphosphate; D000604:Amino Acyl-tRNA Synthetases; D001226:Aspartate-tRNA Ligase; C029194:asparaginyl-tRNA synthetase