Figure 6. Inter- and intramolecular FRET indicates MITF C-end IDRs are proximal to each other and dynamic.

(A, B) Single-molecule Förster resonance energy transfer histograms of dimeric MITF fluorescently labeled at residues C306 and C419. Intermolecular FRET (A) showing fitted Gaussian population mean, E = 0.66, and intramolecular FRET (B), showing fitted Gaussian population mean, E = 0.3. FRET populations fitted with a Gaussian distribution are indicated in blue with donor-only events in grey. (C) Fluorescence lifetime analysis of inter- and intramolecular distances of the C-terminal IDR of MITF. The 2-D plot shows the lifetime of the donor in the presence of the acceptor $\left({\tau }_D^{FRET}\right)$ relative to the donor fluorescence in its absence $\left({\tau }_D^{Donly}\right)$, plotted against the FRET transfer efficiency for each burst. The solid black line shows the expected relationship for a static distance, while the grey line shows the expected relationship for a dynamic chain with a Gaussian distribution of distances. Source data are available online for this figure.