The structure-based sequence alignment of the receptors transmembrane domains was obtained from the GPCRdb website.

Based on the alignment, we built and plotted the fan tree with R. In particular, we calculated a pairwise distance matrix based on identity through the seqinr package. Subsequently, we built the fan tree with the hclust function (Ward method) and plotted it with the plot function of the ape package, as expanded by the phyloch package.