title: Association of alpha-subunits with nucleotide-modified beta-subunits induces asymmetry in the catalytic sites of the F1-ATPase alpha3beta3-hexamer.
abstract: The photoaffinity spin-labeled ATP analog, 2-N3-SL-adenosine triphosphate (ATP), was used to covalently modify isolated beta-subunits from F1-ATPase of the thermophilic bacterium PS3. Approximately 1.2 mol of the nucleotide analog bound to the isolated subunit in the dark. Irradiation leads to covalent incorporation of the nucleotide into the binding site. ESR spectra of the complex show a signal that is typical for protein-immobilized radicals. Addition of isolated alpha-subunits to the modified beta-subunits results in ESR spectra with two new signals indicative of two distinctly different environments of the spin-label, e.g., two distinctly different conformations of the catalytic sites. The relative ratio of the signals is approx 2:1 in favor of the more closed conformation. The data show for the first time that when nucleotides are bound to isolated beta-subunits, binding of alpha-subunits induces asymmetry in the catalytic sites even in the absence of the gamma-subunit.
authors.affiliation: Fachbereich Chemie der Universität Kaiserlautern, Erwin Schrödinger Strasse, 67663 Kaiserslautern, Germany.
authors.forename: Sabine
authors.initials: S
authors.lastname: Burgard
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Harada
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Kagawa
authors.forename: Wolfgang E
authors.initials: WE
authors.lastname: Trommer
authors.forename: Pia D
authors.initials: PD
authors.lastname: Vogel
mesh_terms: D000244:Adenosine Diphosphate / Q000737:chemistry; D025243:Bacterial Proton-Translocating ATPases / Q000737:chemistry*; D020134:Catalytic Domain; D004578:Electron Spin Resonance Spectroscopy; D011487:Protein Conformation; D017510:Protein Folding; D021122:Protein Subunits / Q000737:chemistry*; D013113:Spin Labels
chemical_list: D021122:Protein Subunits; D013113:Spin Labels; D000244:Adenosine Diphosphate; D025243:Bacterial Proton-Translocating ATPases