Extended Data Fig. 3: Biochemical and negative-stain electron microscopy analysis.
From: Structure and assembly of the mitochondrial membrane remodelling GTPase Mgm1
a, Liposome-binding assays (see also Figs. 1c, 2d) and quantification for Mgm1 mutants. Error bars indicate s.d. of 4 independent measurements. b, Isothermal titration calorimetry experiments showing binding of GTPγS to Mgm1 with a Kd of 9 ± 3 µM, binding number n = 1.01, deviation represents root-mean-square (r.m.s.) error of the fit (n = 1). c, Sedimentation equilibrium of wild-type Mgm1 (black) and Mgm1(F840D) (red) was performed at a protein concentration of 1 mg ml−1 at 8,000 r.p.m. and 20 °C. The protein distribution in the cell was monitored by absorbance at 280 nm. Solid lines represent fits to a molecular mass of Mr = 146 ± 6 kDa for wild-type Mgm1 and 78 ± 5 kDa for the Mgm1(F840D) (deviation represents r.m.s. error of the fit), indicating dimeric and monomeric association states at given conditions. The upper panel shows the original data and fits, the lower panels show the residuals from fit to data. d, GTPase assays using HPLC analysis. Error bars show s.d. of the mean of 4 independent experiments (each with 4 or 5 data points). e, Control experiments for negative-stain electron microscopy analysis of Mgm1-mediated membrane remodelling. Scale bars, 200 nm. f, Mgm1 binds to liposomes and forms tubes of different diameters with or without nucleotides present. Scale bars, 100 nm. g, Representative electron micrographs for Mgm1 mutants. Proteins with mutations in dimer interface-2 (F840D), in the membrane-binding site (R748A/K749A), the disulfide bond in the paddle domain (C812S and C821S) or in the putative paddle–paddle contact (F779D/S780D) show severe defects in tube formation or in the assembly of a regular liposome decoration compared to Mgm1. Scale bars, 100 nm. n = 2 independent experiments for e–g.
