Fig. 5: Structure of the S. venezuelae GlgX-c-di-GMP complex.
From: Allosteric regulation of glycogen breakdown by the second messenger cyclic di-GMP
a Ribbon diagram of the S. venezuelae GlgX-c-di-GMP complex with one GlgX subunit colored cyan and the other salmon. Shown as sticks are the c-di-GMP molecules bound at each end of the antiparallel dimer. Also displayed over the structure is the mFo-DFc omit map, shown as a blue mesh and contoured at 4.2 σ in which the c-di-GMP molecules had been removed prior to multiple rounds of refinement. There was clear density for each c-di-GMP molecule. b Close up of the GlgX-c-di-GMP binding interaction. Key residues mediating contacts to the c-di-GMP are shown as sticks and labeled. Hydrogen bonds from GlgX residues that specify binding to the guanine are indicated by yellow dashed lines. c Fluorescence polarization (FP) binding isotherm showing interaction of GlgX, GlgXE47A-R49A and GlgXR438A-R579A for F-c-di-GMP in red, green and blue respectively. Also shown is the binding isotherm for GlgX binding to F-c-di-AMP in black. WT GlgX-bound F-c-di-GMP with a Kd of 8.2 ± 1.0 μM while the mutants showed nonsaturable binding and WT GlgX also did not bind F-c-di-AMP. The y-axis and x-axis are millipolarization (mP) units and GlgX concentration (μM), respectively. Shown are representative binding curves for each. The experiments were performed in technical triplicates and the error between measurements reported. Error bars represent SD of the measurements. Source data are provided in the Source data file.
