Figure 3. Comparison of ¹H-¹⁵N HSQC spectra of ¹⁵N-labeled TAZ1 in complex with CITED2, HIF-1α, and the fusion peptide.

(A) Regions of superimposed ¹H-¹⁵N HSQC spectra (900 MHz ¹H frequency) of ¹⁵N-labeled TAZ1 bound to unlabeled CITED2 (green), HIF-1α (red), or fusion peptide (blue). Backbone amide cross peaks corresponding to TAZ1 α₄ helix residues A435 (left panel) and S436 (right panel) are labeled. (B) Weighted average ¹H,¹⁵N chemical shift differences for ¹⁵N-TAZ1 (Δδ_ave=[(Δδ_HN)²+(Δδ_N/5)²]^½) between the CITED2 and fusion peptide complexes (green) and between the HIF-1α and fusion peptide complexes (red). Circles denote residues for which backbone amide resonance assignments are missing for the CITED2 (green), HIF-1α (red), and fusion peptide (blue) complexes. Residues for which there are no circles and no data are prolines. Boxes above the plot indicate the positions of the TAZ1 α₁ − α₄ helices in the TAZ1:fusion peptide crystal structure; the broken lines indicate the length of the α₄ helix in the TAZ1:CITED2 structure. The broken green and red lines inside the graph denote one standard deviation above the 10 % trimmed mean for the TAZ1:CITED2 Vs. TAZ1:fusion peptide and TAZ1:HIF-1α Vs. TAZ1:fusion peptide data sets, respectively. (C) Structure of the TAZ1:fusion peptide complex, with TAZ1 shown in salmon and the fusion peptide in slate. TAZ1 α₁ residues for which backbone amide ¹H-¹⁵N HSQC cross peak intensity is reduced by greater than 60 % in the fusion peptide complex compared to the CITED2 complex are shown as red spheres. Fusion peptide α_A and α_C residues for which backbone amide resonances are broadened beyond detection or have normalized cross peak intensity less than 0.2 (see Figure 4B) are shown as cyan spheres. Zn atoms are omitted for clarity.