Fig. 4: Dynamic FtsZ-YFP-mts rings exert forces in the pN range.

a Spring-like structures (N = 36) were mechanically assessed by forcing the tube length to oscillate with an amplitude of 3 μm and a frequency of \(1\,{{\mathrm{Hz}}}\). To measure a reliable force contribution from the protein, we increased the protein sample concentration (see “Methods”) to guarantee a full/high protein coverage of the tube. b To measure forces, we tracked bead-displacement as response of the dynamic input. Then we Fast Fourier-transformed (FFT) the data to calculate the amplitude of the signal. Magenta line: lipid signal and green line: FtsZ. c Spontaneous flattening of vesicles over the glass surface permitted to characterize the total brightness of single rings (N = 412) with exactly same conditions as lipid tube experiments. d By calculating the amplitude of each FFT force signal (b), we assessed the spring constant for the case of the only lipid contribution (N = 11) and FtsZ (N = 36). Dashed magenta lines indicate the range where the lipid response dominated over the FtsZ contribution to the spring constant. (d—insert) The total FtsZ brightness for each data point in (d) was determined to approximate the FtsZ brightness-per-ring in accordance with Fig. S2E. Thus, the distribution of forces/ FtsZ brightness-per-ring was plotted (N = 23) showing a mean value around 1 pN per ring unit. (Scale bar = 2 µm).