title: The use of double mutants to detect structural changes in the active site of the tyrosyl-tRNA synthetase (Bacillus stearothermophilus).
abstract: In a previous study, a mutant of tyrosyl-tRNA synthetase in which a threonine residue (Thr51) was converted to proline dramatically improved the affinity of the enzyme for its ATP substrate. How does Pro51 improve the enzyme's affinity for ATP? A priori, Pro51 might interact directly with the ATP, or it might distort the polypeptide backbone and thereby force new or improved contacts elsewhere from the enzyme to ATP. By making mutants of the Pro51 enzyme at two residues that make hydrogen bonds to the ATP substrate, we show that Pro51 greatly improves the strength of one of these contacts. Thus the propagation of a structural change in an enzyme induced by mutation may be detected by the introduction of further mutations.
mesh_terms: D000604:Amino Acyl-tRNA Synthetases / Q000235:genetics*; D001665:Binding Sites; D005798:Genes, Bacterial; D001411:Geobacillus stearothermophilus / Q000201:enzymology* / Q000235:genetics; D007700:Kinetics; D008958:Models, Molecular; D009154:Mutation; D009693:Nucleic Acid Hybridization; D011487:Protein Conformation; D014448:Tyrosine-tRNA Ligase / Q000235:genetics* / Q000378:metabolism
chemical_list: D000604:Amino Acyl-tRNA Synthetases; D014448:Tyrosine-tRNA Ligase