Figure 3: Conformational dynamics in the GD-BSE region.

(a) Histograms of FRET data from the mutant MxA^MO2-AS in different nucleotide-loading conditions. Error bars indicate s.d. of 1,000 bootstrap samples of the FRET traces. Decomposition of the FRET data resulted in two Gaussian curves representing distributions of a low-FRET state (red) and a high-FRET state (green). The number of molecules (N) of smFRET trajectories used to construct each histogram is displayed. (b) Crystal structures of stalkless MxA (left) and dynamin-1 (right) showing the corresponding distances in different nucleotide-loading forms. For MxA, apo (4P4U, green), GMPPCP-bound (4P4S, wheat) and GDP-bound (4P4T, cyan) forms are shown, and distances between amino acid residues 149 and 639 (634 is missing in these structural models) were measured. For dynamin, apo (3SNH, green), GMPPCP-bound (3ZYC, wheat), GDP·AlF₄⁻-bound (2X2E, magenta) forms are shown, distances between residues 107 and 726 were measured according to the sequence alignment with MxA. (c) Fraction variation in the low-FRET open state (red circle) and the high-FRET closed state (green circle) during GTP hydrolysis. Two GTP hydrolysis cycles are depicted. (d) Representative fluorescence and FRET time traces with idealization (orange) in corresponding nucleotide-loading conditions. Here, FRET traces were idealized to a model containing four states corresponding to Gaussian decomposition shown in a. (e) TDPs in different nucleotide-loading conditions. Initial and final FRET (average FRET values before and after each transition respectively) were plotted as a 2D chart to indicate the transitions between the two distinct FRET states (scale at right). (f) Average dwell times in each FRET state in different nucleotide-loading conditions. Error bars indicate s.d. of 100 bootstrap samples. (g) Cross-correlation analysis shows enhanced dynamics for GMPPCP-loading condition while limited dynamics for the other three conditions. Error bars indicate s.d. of results from five independent experiments. 2D, two-dimensional; TDP, transition density plot.