Extended Data Fig. 1: Helical wheel for coiled coil DHT01 and mutations at position g affect ABC assembly.

a Shared interfaces of all three chains of the heterotrimer are broken up by heptads and helical wheel positions, with the amino acid letters in bold indicating the residues found by Monte Carlo HBNet. Residues contributing to the designed hydrogen bond networks are found at a, d, e, and g positions. b A helical wheel was drawn for each chain and then combined to form a heterotrimer wheel, with positions color-coded to indicate the presence of nonpolar, polar, or mixed (nonpolar and polar) residues. Letters in bold again match the residues found by Monte Carlo HBNet. c A helical wheel for a heterotrimer variant that now has only polar residues at position g for chains A and B, with respective mutations colored by chain (gray for A, blue for B). Experimental validation of this design by LC-MS indicates the absence of chain B in the IMAC pull-down eluate. d Three mutations of the variant heterotrimer from c are shown in cartoon and stick representation, with the mutated amino acid colored in white. It was hypothesized that polar or charged amino acids could help contribute to ionic interactions, which were found to be important for mediating specificity in PDB 1BB1, a previously designed ABC coiled coil peptide³. One example of an ionic interaction designed for this peptide is shown to the lower right, as determined by a 1.8 Å x-ray crystal structure.