Figure S3.

Cholesterol sensing by TRKB, related to Figures 1 and 3

(A) The distribution of the distance between the C-terminal residues of the monomers (center of mass L451-L453 Cα atoms (indicated with an arrow in Figure 1) are shown as violin plots. Increasing cholesterol concentration increases membrane thickness, which for the wild-type decreases the C-terminal distance. Y433F results in the disruption of the dimerization interface and the cross-like conformation. The parallel-like conformation of the WT-Y433F dimer appears to have a smaller hydrophobic length than that of the individual WT helices. Given at the bottom are average values for the membrane thickness (phosphate-phosphate distance) and the average angle between the helices ɑ. [Kruskal-Wallis: H = 27.8736; p < 0.001; n = 10/group]. (B) The effect of cholesterol concentration and the Y433F mutation on the stability of the interdimeric interface. The stability of the dimerization interface is characterized by a distribution of the distance between the monomers’ Cα carbons of G443 shown as violin plots for wild-type at different cholesterol concentrations and for the Y433F heterozygous mutant at 20 mol% cholesterol concentration (systems 1-4, Table S1) [Kruskal-Wallis: H = 25.4385; p < 0.001; n = 10/group]. The results demonstrate that the Y433F mutation results in a total disruption of the A439-G443 dimerization interface. (C) The distribution of the distance between the C-terminal residues of the monomers (center of mass L439-L437 Cα atoms) in the TRKA transmembrane domain shown as violin plots. The results indicate that cholesterol concentration has no notable effect on the distance between the C-terminal residues of the two monomers in the TRKA TM dimer. In essence, TRKA is non-responsive to changes in cholesterol concentration (systems 12-14, Table S1).