title: tRNAGlu increases the affinity of glutamyl-tRNA synthetase for its inhibitor glutamyl-sulfamoyl-adenosine, an analogue of the aminoacylation reaction intermediate glutamyl-AMP: mechanistic and evolutionary implications.
abstract: For tRNA-dependent protein biosynthesis, amino acids are first activated by aminoacyl-tRNA synthetases (aaRSs) yielding the reaction intermediates aminoacyl-AMP (aa-AMP). Stable analogues of aa-AMP, such as aminoacyl-sulfamoyl-adenosines, inhibit their cognate aaRSs. Glutamyl-sulfamoyl-adenosine (Glu-AMS) is the best known inhibitor of Escherichia coli glutamyl-tRNA synthetase (GluRS). Thermodynamic parameters of the interactions between Glu-AMS and E. coli GluRS were measured in the presence and in the absence of tRNA by isothermal titration microcalorimetry. A significant entropic contribution for the interactions between Glu-AMS and GluRS in the absence of tRNA or in the presence of the cognate tRNAGlu or of the non-cognate tRNAPhe is indicated by the negative values of -TΔSb, and by the negative value of ΔCp. On the other hand, the large negative enthalpy is the dominant contribution to ΔGb in the absence of tRNA. The affinity of GluRS for Glu-AMS is not altered in the presence of the non-cognate tRNAPhe, but the dissociation constant Kd is decreased 50-fold in the presence of tRNAGlu; this result is consistent with molecular dynamics results indicating the presence of an H-bond between Glu-AMS and the 3'-OH oxygen of the 3'-terminal ribose of tRNAGlu in the Glu-AMS•GluRS•tRNAGlu complex. Glu-AMS being a very close structural analogue of Glu-AMP, its weak binding to free GluRS suggests that the unstable Glu-AMP reaction intermediate binds weakly to GluRS; these results could explain why all the known GluRSs evolved to activate glutamate only in the presence of tRNAGlu, the coupling of glutamate activation to its transfer to tRNA preventing unproductive cleavage of ATP.
authors: Département de Biochimie, de Microbiologie et de Bio-informatique, Université Laval, Québec, Canada; Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec, Canada; The Quebec Network for Research on Protein Function, Structure, and Engineering (PROTEO), Québec, Canada.
authors: Sébastien P
authors: SP
authors: Blais
authors: Department of Biology, Centre for Structural and Functional Genomics, Faculty of Arts and Science, Concordia University, Montréal, Canada.
authors: Jack A
authors: JA
authors: Kornblatt
authors: Département de Biochimie, de Microbiologie et de Bio-informatique, Université Laval, Québec, Canada; Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec, Canada; Département de Chimie, Université Laval, Québec, Canada; The Quebec Network for Research on Protein Function, Structure, and Engineering (PROTEO), Québec, Canada.
authors: Xavier
authors: X
authors: Barbeau
authors: Département de Biochimie, de Microbiologie et de Bio-informatique, Université Laval, Québec, Canada; Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec, Canada; The Quebec Network for Research on Protein Function, Structure, and Engineering (PROTEO), Québec, Canada.
authors: Guillaume
authors: G
authors: Bonnaure
authors: Département de Biochimie, de Microbiologie et de Bio-informatique, Université Laval, Québec, Canada; Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec, Canada; The Quebec Network for Research on Protein Function, Structure, and Engineering (PROTEO), Québec, Canada.
authors: Patrick
authors: P
authors: Lagüe
authors: Département de Chimie, Université Laval, Québec, Canada; The Quebec Network for Research on Protein Function, Structure, and Engineering (PROTEO), Québec, Canada.
authors: Robert
authors: R
authors: Chênevert
authors: Département de Biochimie, de Microbiologie et de Bio-informatique, Université Laval, Québec, Canada; Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec, Canada; The Quebec Network for Research on Protein Function, Structure, and Engineering (PROTEO), Québec, Canada.
authors: Jacques
authors: J
authors: Lapointe
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000378:metabolism; D000249:Adenosine Monophosphate / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000378:metabolism; D000595:Amino Acid Sequence; D049148:Aminoacylation; D001665:Binding Sites; D002151:Calorimetry; D004926:Escherichia coli / Q000201:enzymology; D005975:Glutamate-tRNA Ligase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005971:Glutamates / Q000737:chemistry / Q000378:metabolism*; D006860:Hydrogen Bonding; D007700:Kinetics; D062105:Molecular Docking Simulation; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D012352:RNA, Transfer, Glu / Q000378:metabolism*; D016415:Sequence Alignment; D013696:Temperature; D013816:Thermodynamics
chemical_list: C000606314:5'-O-(N-(glutamyl)sulfamoyl)adenosine; D005971:Glutamates; D012352:RNA, Transfer, Glu; D000249:Adenosine Monophosphate; D005975:Glutamate-tRNA Ligase; D000241:Adenosine