Superimposition of KsgA, Dim1, and sc-mtTFB. KsgA (PDB ID: 1QYR) is shown in blue, Dim1 (PDB ID 1ZQ9; A. Dong, H. Wu, H. Zeng, P. Loppnau, M. Sundstrom, C. Arrowsmith, A. Edwards, A. Bochkarev and A. Plotnikov, unpublished data) in orange, and sc-mtTFB (PDB ID: 1I4W) in green. These colors are retained in all figures. In each protein, the backbone was broken in the flexible linker between the N- and C-terminal domains (indicated by dashed lines); the two domains were separately aligned with KsgA using all residues in the domain. All figures were generated using the program Pymol .