Fig. 6: Statistical analysis of MFS proteins to gauge applicability of the BRIL fusion strategy to MFS transporters.

a Histogram plot of the length of the C-terminal tail following the terminal TM helical residue in the structure of 1,118 MFS proteins. Note that 54 proteins displayed tail lengths >120 residues and are not shown. b, d, f AlphaFold2 pLDDT values plotted as a function of residues following the terminal TM helix for a total of 100 MFS structures. The residue after the terminal TM helix was renumbered as residue 1. Using this nomenclature, proteins with no pLDDT values above 70 after residue 4 clustered into the 50% category displayed in (b). Proteins with pLDDT values above 70 for residues 5 —14 clustered into the 25% category displayed in (d). Proteins with pLDDT values above 70 for residues 15 and beyond clustered into the 25% category displayed in (f). The dotted line indicates the pLDDT value of 70, which is the “confident” cutoff used in AlphaFold2. c, e, g Example AlphaFold2 predicted structures for each of the categories in b, d, and f. Each protein is indicated by the Uniprot ID. All residues up to and including the terminal TM helix are colored in gray. Residues with pLDDT values above 70 are colored in blue and those below 70 are colored in magenta, as indicated in the schematic above (c). In each predicted structure, TM12 and the C-terminus is indicated. h Plot of the estimated applicability of the BRIL method presented in this work as a function of different MFS subfamilies. Bars display the percentage of proteins within each subfamily with no pLDDT values above 70 after residue 4 (like those in b). The error bars represent the upper limit percentage of proteins with pLDDT values above 70 only for residues 5 to 14 (like those in (d)). A complete list of MFS subfamilies and applicability is displayed in Supplementary Table 2.