(A) Overall structure of the Tse6282-CT–Tsi6 complex. Tse6282-CT is shown in ribbon (left) and space-filling (right) representations. Secondary structure elements are labeled. Dots denote a disordered segment (amino acids 400–408) of Tse6282-CT that was not modeled.
(B) Tse6282-CT resembles mART toxins. Structural alignment of Tse6282-CT with the catalytic domain of diphtheria toxin (PDB: 4AE1). Inset shows a structural alignment of the three conserved NAD+ binding residues (circled numbers) of diphtheria toxin and Tse6. The numbers correspond to amino acid positions within Tse6.
(C) Tsi6 interacts with the putative NAD+ binding pocket of Tse6. Structural alignment of free Tsi6 and Tsi6 bound to Tse6282-CT. The structure of Tsi6 does not change significantly upon complex formation (e.g., Glu63), except for Lys62, which rotates ~120° and interacts with Gln413 of Tse6.
See also Figure S1 and Tables S1–S3.