Figure 4.

Assigned ¹H-¹⁵N HSQC spectrum and secondary structure probabilities of Alk1-ED. (A) ¹H-¹⁵N HSQC spectrum of 0.4 mM ¹⁵N Alk1-ED in 25 mM sodium phosphate, 0.02% sodium azide, 5% ²H₂O (pH 5.5) recorded at 32 °C at a magnetic field strength of 16.4 T (700 MHz ¹H). Peaks are labeled according to their resonance assignments (residues are number as in Fig. 1). Horizontal dashed bars designate the side-chain amide groups of asparagine and glutamine. (B) Secondary structure probabilities based on an analysis of the NMR secondary shifts using the program PECAN (47). (C) Secondary structure predictions for Alk1 based on the structures of the unbound and bound forms of Alk3 (PDB 2K3G and 1REW, respectively) and an alignment of the Alk1 and Alk3 amino acid sequences.