title: Binding of Mg2+ to the beta subunit or F1 of H+-ATPase from Escherichia coli.
abstract: The bindings of Mg2+ to the F1 portion of Escherichia coli H+-ATPase and its isolated alpha and beta subunits were studied with 8-anilinonaphthalene-1-sulfonate (ANS). The fluorescence of ANS increased upon addition of F1 or its alpha subunit or beta subunit, as reported previously (M. Hirano, K. Takeda, H. Kanazawa, and M. Futai (1984) Biochemistry 23, 1652-1656). The fluorescence of ANS bound to F1 or its beta subunit increased significantly with further addition of Mg2+, whereas that of the alpha subunit increased only slightly. Ca2+ and Mn2+ had similar effects on the fluorescence of ANS with F1 and its beta subunit. The Mg2+-induced fluorescence enhancement (delta F) was high at an alkaline pH and was lowered by addition of ethylenediaminetetraacetic acid. Dicyclohexylcarbodiimide and azide had no effect on the delta F. Binding analysis showed that the concentration dependence of Mg2+ on the fluorescence enhancement of the beta subunit is similar to that of F1. These results suggest that both the beta subunit and F1 have binding sites for Mg2+ and that the delta F observed with F1 may be due to the binding of Mg2+ to the beta subunit.
mesh_terms: D000817:Anilino Naphthalenesulfonates; D001665:Binding Sites; D004926:Escherichia coli / Q000378:metabolism*; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism*; D011487:Protein Conformation; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
chemical_list: D000817:Anilino Naphthalenesulfonates; C027132:1-anilino-8-naphthalenesulfonate; D006180:Proton-Translocating ATPases; D008274:Magnesium