Supplementary Figure 1: Alignment of Axin RGS domains and structural consequences of mutation-induced destabilization.

(a) Alignment of Axin RGS domain amino acid sequences of Homo sapiens and other indicated species. Mutated residues found in cancer patients are indicated in red and show full, partial or no conservation. (b) CD spectra of purified wild-type (WT) and mutant RGS domains are shown at the indicated temperatures. At low temperatures all CD spectra, with the exception of RGS-L106R, exhibit typical α-helical profiles showing two peak minima at 208 and 220 nm and a peak maximum at 190 nm. For each of these mutants, loss of α-helical structure is shown at or above the unfolding temperature that were calculated from fluorescence-based thermal denaturation (Fig. 1f). CD spectra of RGS-L106R do not display α-helical content and remain unaffected by temperature change. Results represent two independent experiments. (c) 2D NMR spectra showing signals of RGS-L106R. As compared to the 2D NMR spectrum of RGS-wt (Fig. 3b), Trp side chain signals (purple squares) as well as signals from folded regions (grey squares) are lost for RGS-L106R, indicating loss of regular 3D structure. By contrast, signals from disordered termini of the protein remain in place (blue squares).