title: Calorimetric assessment of Fe(2+) binding to α-ketoglutarate/taurine dioxygenase: ironing out the energetics of metal coordination by the 2-His-1-carboxylate facial triad.
abstract: The thermodynamic properties of Fe(2+) binding to the 2-His-1-carboxylate facial triad in α-ketoglutarate/taurine dioxygenase (TauD) were explored using isothermal titration calorimetry. Direct titrations of Fe(2+) into TauD and chelation experiments involving the titration of ethylenediaminetetraacetic acid into Fe(2+)-TauD were performed under an anaerobic environment to yield a binding equilibrium of 2.4 (±0.1) × 10(7) (Kd = 43 nM) and a ΔG° value of -10.1 (±0.03) kcal/mol. Further analysis of the enthalpy/entropy contributions indicates a highly enthalpic binding event, where ΔH = -11.6 (±0.3) kcal/mol. Investigations into the unfavorable entropy term led to the observation of water molecules becoming organized within the Fe(2+)-TauD structure.
authors: Department of Chemistry, Mississippi State University , Mississippi State, Mississippi 39762, United States.
authors: Kate L
authors: KL
authors: Henderson
authors: Tina A
authors: TA
authors: Müller
authors: Robert P
authors: RP
authors: Hausinger
authors: Joseph P
authors: JP
authors: Emerson
mesh_terms: D001665:Binding Sites; D002151:Calorimetry; D002264:Carboxylic Acids / Q000737:chemistry*; D049308:Dioxygenases / Q000737:chemistry* / Q000378:metabolism; D005296:Ferrous Compounds / Q000737:chemistry* / Q000378:metabolism; D006639:Histidine / Q000737:chemistry*; D007656:Ketoglutaric Acids / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D015394:Molecular Structure; D013654:Taurine / Q000737:chemistry* / Q000378:metabolism; D013816:Thermodynamics
chemical_list: D002264:Carboxylic Acids; D005296:Ferrous Compounds; D007656:Ketoglutaric Acids; D013654:Taurine; D006639:Histidine; D049308:Dioxygenases