Department of Molecular Biology, Cell Biology, & Biochemistry, Brown University, Providence, Rhode Island, USA.
Department of Chemistry, Yale University, New Haven, Connecticut, USA.
J Biol Chem. 2021 Sep;297(3):101061. doi: 10.1016/j.jbc.2021.101061. Epub 2021 Aug 9.
The macrophage migration inhibitory factor (MIF) family of cytokines contains multiple ligand-binding sites and mediates immunomodulatory processes through an undefined mechanism(s). Previously, we reported a dynamic relay connecting the MIF catalytic site to an allosteric site at its solvent channel. Despite structural and functional similarity, the MIF homolog D-dopachrome tautomerase (also called MIF-2) has low sequence identity (35%), prompting the question of whether this dynamic regulatory network is conserved. Here, we establish the structural basis of an allosteric site in MIF-2, showing with solution NMR that dynamic communication is preserved in MIF-2 despite differences in the primary sequence. X-ray crystallography and NMR detail the structural consequences of perturbing residues in this pathway, which include conformational changes surrounding the allosteric site, despite global preservation of the MIF-2 fold. Molecular simulations reveal MIF-2 to contain a comparable hydrogen bond network to that of MIF, which was previously hypothesized to influence catalytic activity by modulating the strength of allosteric coupling. Disruption of the allosteric relay by mutagenesis also attenuates MIF-2 enzymatic activity in vitro and the activation of the cluster of differentiation 74 receptor in vivo, highlighting a conserved point of control for nonoverlapping functions in the MIF superfamily.
巨噬细胞移动抑制因子(MIF)细胞因子家族包含多个配体结合位点,并通过未知机制(多种机制)介导免疫调节过程。此前,我们报道了一种动态接力,将 MIF 催化位点连接到其溶剂通道的变构位点。尽管结构和功能相似,但 MIF 同源物 D-多巴色素互变异构酶(也称为 MIF-2)的序列同一性(35%)较低,这引发了一个问题,即这种动态调节网络是否保守。在这里,我们建立了 MIF-2 中变构位点的结构基础,通过溶液 NMR 表明,尽管在一级序列上存在差异,但动态通讯在 MIF-2 中得以保留。X 射线晶体学和 NMR 详细说明了该途径中扰动残基的结构后果,包括变构位点周围的构象变化,尽管 MIF-2 折叠保持全局。分子模拟揭示了 MIF-2 含有与 MIF 相当的氢键网络,这一假设之前被认为通过调节变构偶联的强度来影响催化活性。通过突变破坏变构接力也会减弱 MIF-2 在体外的酶活性和体内 CD74 受体的激活,突出了 MIF 超家族中非重叠功能的保守控制点。