PDB ID 5DJZ. Rosetta mispredicted the rotamer adopted by A_D399M, but even the crystal rotamer would be close enough to b_K409 to collide, either pushing it unfavorably towards a_K370, or pushing it away from aK370 but still disrupting the solvation shell surrounding b_K409. In any case, A_D399M consistently increased heterodimer purity when paired with other family 7 mutations. Rosetta correctly identified the rotamers for B_T366V and B_K409V, which both adopt the most commonly seen β-sheet rotamer. Surprisingly, the backbone for B_T366V moved away from the center of the interface by 0.5Å, enlarging the cavity left by A_Y407A, which is incompletely filled by B_K409V. The interface-residue heavy-atom RMSD between the two structures is 0.86 Å.