Extended Data Fig. 11: Na⁺ ion utilization by DISP1, PTCH1, and other members of the RND transporter family.

a, Close-up views of Na⁺ ion sites I, II, and III in DISP1, showing the locations of liganding oxygens from amino acid side chains and main-chain carbonyls (see main text), and of the corresponding locations in PTCH1³⁵ (PDB ID: 6RMG), based on structural alignment of the two proteins. Note the presence in both proteins of a charge-neutralizing acidic residue at each site, and the conservation of side-chain oxygens as ligands. b, Structural alignment, using Chimera Matchmaker, of RND family members, including DISP1, PTCH1, NPC1, and several prokaryotic RND transporters. c, Tabulated conservation of charge-neutralizing residues (3 total) or oxygen ligands from amino acid side-chains (10 total) in the indicated proteins, aligned from structure (b, see PDB IDs from the second right column) or, if possible without ambiguity, aligned from sequence. References to specific sequences, structures, or background information are given within the table, including refs .^{1,2,6,24,27,32,35,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71}. Note the close conservation of Na⁺-liganding side-chains and charge-neutralizing residues in PTCH1, known to require Na⁺ for its activity, and in Disp from Drosophila melanogaster. The prokaryotic Na⁺-utilizing SecD1/SecF1 peptide translocator from Vibrio alginolyticus (encoded as two peptides; aligned by homology to Thermus thermophilus SecDF), in contrast, appears to have evolved a distinct mode of Na⁺ interaction. See Supplementary Discussion. Abbreviations: Mmus, Mus musculus; Dmel, Drosophila melanogaster; Hsap, Homo sapiens; Ecol, Escherichia coli; Paer, Pseudomonas aeruginosa; Cjej, Campylobacter jejuni; Abau, Acinetobacter baumannii; Msme, Mycolicibacterium smegmatis; Bmul, Burkholderia multivorans; Tthe2, Thermus thermophilus; Valg, Vibrio alginolyticus.