title: Isolated noncatalytic and catalytic subunits of F1-ATPase exhibit similar, albeit not identical, energetic strategies for recognizing adenosine nucleotides.
abstract: The function of F1-ATPase relies critically on the intrinsic ability of its catalytic and noncatalytic subunits to interact with nucleotides. Therefore, the study of isolated subunits represents an opportunity to dissect elementary energetic contributions that drive the enzyme's rotary mechanism. In this study we have calorimetrically characterized the association of adenosine nucleotides to the isolated noncatalytic α-subunit. The resulting recognition behavior was compared with that previously reported for the isolated catalytic β-subunit (N.O. Pulido, G. Salcedo, G. Pérez-Hernández, C. José-Núñez, A. Velázquez-Campoy, E. García-Hernández, Energetic effects of magnesium in the recognition of adenosine nucleotides by the F1-ATPase β subunit, Biochemistry 49 (2010) 5258-5268). The two subunits exhibit nucleotide-binding thermodynamic signatures similar to each other, characterized by enthalpically-driven affinities in the μM range. Nevertheless, contrary to the catalytic subunit that recognizes MgATP and MgADP with comparable strength, the noncatalytic subunit much prefers the triphosphate nucleotide. Besides, the α-subunit depends more on Mg(II) for stabilizing the interaction with ATP, while both subunits are rather metal-independent for ADP recognition. These binding behaviors are discussed in terms of the properties that the two subunits exhibit in the whole enzyme.
authors.affiliation: Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, México 04510, D.F., Mexico.
authors.forename: Guillermo
authors.initials: G
authors.lastname: Salcedo
authors.forename: Patricia
authors.initials: P
authors.lastname: Cano-Sánchez
authors.forename: Marietta Tuena
authors.initials: MT
authors.lastname: de Gómez-Puyou
authors.forename: Adrián
authors.initials: A
authors.lastname: Velázquez-Campoy
authors.forename: Enrique
authors.initials: E
authors.lastname: García-Hernández
mesh_terms: D000241:Adenosine / Q000737:chemistry* / Q000378:metabolism; D000244:Adenosine Diphosphate / Q000737:chemistry / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D002151:Calorimetry; D020134:Catalytic Domain; D004268:DNA-Binding Proteins / Q000737:chemistry; D004734:Energy Metabolism; D004926:Escherichia coli / Q000201:enzymology; D007700:Kinetics; D008274:Magnesium / Q000737:chemistry / Q000378:metabolism; D009711:Nucleotides / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D013816:Thermodynamics
chemical_list: D004268:DNA-Binding Proteins; D009711:Nucleotides; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases; D008274:Magnesium; D000241:Adenosine
keywords: 2-amino-2-(hydroxymethyl)propane-1,3-diol; ADP; ATP; ATPase; Binding energetics; EDTA; EF1; F(1)-ATPase; F1 sector from Bacillus PS3; F1 sector from Escherichia coli; Heterotropic cooperativity; ITC; Isolated subunit; Isothermal titration calorimetry; K(N1) and K(N2); K(Pf) and K(Pb); K(b); K(d); Metal binding; Mg(II); MgCl2; NMR; S1, S2 and S3; TF1; Tris; adenosine 5′-diphosphate; adenosine 5′-triphosphatase; adenosine 5′-triphosphate; association constants for ATP and Mg·ATP binding to the subunit; binding Gibbs free energy; binding enthalpy; binding entropy; cooperative Gibbs free energy; cooperative enthalpy; cooperative entropy; cooperative heterotropic association constant; equilibrium binding constant; equilibrium dissociation constant; ethylenediaminetetraacetic acid; free magnesium ion; high, medium and low affinity β-subunit sites in F1, respectively; isothermal titration calorimetry; magnesium chloride; nuclear magnetic resonance; step-wise association constants for the interaction of ATP with Mg(II); ΔG(b); ΔH(b); ΔS(b); Δg; Δh; Δs; β subunits in the crystal structure of F1 bound to Mg·ADP and Mg·AMPPNP, respectively; βDP and βTP; κ