Figure 5.

NMR evidence for the surfaces by which IscX and IscU interact. (A) Perturbation of the ¹⁵N^H-¹H^N signals (Δδ_NH) of [U-¹⁵N]-IscX, resulting from the addition of 4 equiv of IscU. Red triangles denote residues whose chemical shift changes could not be followed because of severe line broadening. (B) Results from panel A mapped onto the structure of IscX (PDB 2BZT)¹⁷ with the following color code: gray, not affected; blue, significantly shifted (Δδ_NH > 0.04 ppm); red, broadened; black, not assigned or overlapped. (C) Perturbation of the ¹⁵N^H-¹H^N signals of [U-¹⁵N]-IscU resulting from the addition of 4 equiv IscX. Red triangles denote residues whose chemical shift changes could not be followed because of severe line broadening. (D) Results from panel C mapped onto the structure of IscU (PDB 2L4X)³³ with the same color code used for panel B.