Positions of the mutations. (A) Structure of Lmod2s1/αTM1a_1–14Zip complex (PDB ID 6UT2). The section in magenta is the first 14 residues of the Tpm1.1 fragment. The section highlighted in tan is the leucine zipper sequence. The section highlighted in blue is the first 11 residues of the Lmod2 fragment, which were removed in the Δ11 mutation. The section highlighted in cyan represents residues 12–25 of Lmod2s1, and the section highlighted in cornflower blue is the remainder of Lmod2s1 (residues 26–41). The mutated residues are shown in gray, with side chains displayed for clarity. The side chains of all residues that form the hydrophobic core of the complex are shown in the central image, as well as two salt bridges formed by Lmod2’s Asp19 and Glu41 with lysine in αTM1a_1–14Zip. The N and C termini of the Lmod2s1 and the C termini of the αTM1a_1–14Zip dimer are labeled. Inserts show magnified views of the complex in the region of the mutations S24K, S24L, E36V, and E34Q, introduced in Chimera and before MDS. (B) Comparison of the sequences of the Tpm-binding sites for Lmod2 and Lmod3 (a skeletal muscle isoform).