(Top) N-H correlation of Thr 128 (C-terminal residue of helix D), which exhibits slow exchange behavior in the M-IV-MycG titration, monitored by 1H,15N TROSY-HSQC. The correlation is only observed in the absence of M-IV (red) and upon M-IV saturation (black). (Bottom) N-H correlation of Leu 84 (B’-C loop), showing intermediate exchange behavior. Substrate free spectrum is shown in red, 0.5/1 M-IV/MycG in gold and M-IV saturated MycG in black.