Redox-dependent structure and dynamics of macrophage migration inhibitory factor reveal sites of latent allostery

Macrophage migration inhibitory factor (MIF) is a multifunctional immunoregulatory protein that is a key player in the innate immune response. Given its overexpression at sites of inflammation and in diseases marked by increasingly oxidative environments, a comprehensive understanding of how cellular redox conditions impact the structure and function of MIF is necessary. We used NMR spectroscopy and mass spectrometry to investigate biophysical signatures of MIF under varied solution redox conditions. Our results indicate that the MIF structure is modified and becomes increasingly dynamic in an oxidative environment, which may be a means to alter the MIF conformation and functional response in a redox-dependent manner. We identified latent allosteric sites within MIF through mutational analysis of redox-sensitive residues, revealing that a loss of redox-responsive residues attenuates CD74 receptor activation. Leveraging sites of redox sensitivity as targets for structure-based drug design therefore reveals an avenue to modulate MIF function in its "disease state."