Fig. 6: Ligand-free dimer conformers interact via transversal transmembrane contacts.

a Previously proposed transmembrane dimers⁴⁵. Lzip has leucine zipper-like interactions (V⁶³⁵xxL⁶³⁸xxxL⁶⁴²) and could establish contacts with Nter⁺/Nter and Cter⁺/Cter to assemble oligomers. b Top, a speculative tetramer (yellow) from two monomers interacting through Lzip contacts with one Cter interface. A Cter dimer model (magenta) is placed on top of the tetramer showing that the residues in the Cter interface are distinct from Lzip. Bottom, orthogonal projection on xy-plane. (Equivalent for Lzip contacts with one Nter interface in Supplementary Fig. 3f). c, f, g FLImP analysis of 100 separation probability distributions between Affibody-CF640R pairs in the conditions indicated: Sum of posteriors of individual separations between fluorophores (gray background) and abundance-weighted probability distributions of individual components of decomposed separation distribution (colored peaks). Plot legend and bars above colored component distributions give the median and most-compact 68% confidence interval for each. Legend also gives median proportion of measurements assigned to clutter. Stars and dots below show individual separations assigned to peaks (colored) or clutter (black). The median peak positions marked by dashed lines are those of WT-EGFR. d Comparisons between decomposed separation probability distributions between FLImP datasets. The continuous lines show the marginalized separation posterior, i.e. the sum of the abundance-weighted peaks, for each condition in the inset. The fluctuations around each continuous line arise from variations derived from FLImP decompositions for 20 bootstrap-resampled datasets to assess errors due to the finite number of measurements. Dashed lines mark WT-EGFR median peak positions. Colored arrows show shift from WT. e Wasserstein MDS analysis of FLImP decompositions for the conditions in the inset. Similarities or dissimilarities between the 21 separation sets of different conditions (one main FLImP decomposition plus 20 bootstrap-resampled decompositions) are compared. Plot axes are components C1 and C2. C1 represents the dimension that captures the largest amount of variance in the data, while C2 represents the second-largest amount of variance that is orthogonal to C1. The ellipse centers (95% confidence range) mark the positions of the main FLImP decompositions. The crosses mark the positions of individual bootstrap-resampled separation sets.