FIGURE 5.

Mg²⁺-induced conformational change in DgkB. Two methods were used to investigate potential conformational changes in DgkB triggered by Mg²⁺ binding in the absence of lipid. A, SYPRO orange fluorescent dye binding to DgkB decreased as a function of MgCl₂ concentration. The Mg²⁺ dissociation constants calculated from these data were: DgkB, •, 390 ± 13 μm; DgkB[D216A], ▪, 490 ± 32 μm; DgkB[D124A], ○, 780 ± 61 μm; and DgkB[D271A], □, 1060 ± 106 μm. B, intrinsic tryptophan fluorescence of DgkB[Y163W] decreased as a function of MgCl₂ concentration. The apparent dissociation constants for Mg²⁺ were: DgkB[Y163W] (•), 303 ± 72 μm; DgkB[Y163W,D216A] (▪), 845 ± 365 μm; DgkB[Y163W,D124A] (○), 424 ± 285 μm; and DgkB[Y163W,D271A] (□), not detected. Error bars represent S.E.