Number of structural comparisons carried out between -helical membrane protein structures after following the criteria to select structurally related structures described inSTAR Methods. The total number of pairwise alignments is plotted as a function of the number of membrane-spanning regions in the protein chain of interest. Thus, fewer comparisons were carried out for structures with higher numbers of transmembrane helices, reflecting their distribution in the database. To indicate whether each structure is compared to other structures with a similar number of TM helices, the color coding indicates the relative number of TM regions of the second chain in the pair. Structures with 2030 transmembrane helices can undergo thousands of comparisons, while structures with 3055 transmembrane helices undergo <100 comparisons.
