Wesley Nathaniel A, Wachnowsky Christine, Fidai Insiya, Cowan J A
Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, USA.
The Ohio State Biochemistry Program, The Ohio State University, Columbus, OH, USA.
FEBS J. 2017 Nov;284(22):3817-3837. doi: 10.1111/febs.14270. Epub 2017 Oct 16.
Iron-sulfur (Fe/S) clusters are ancient prosthetic groups found in numerous metalloproteins and are conserved across all kingdoms of life due to their diverse, yet essential functional roles. Genetic mutations to a specific subset of mitochondrial Fe/S cluster delivery proteins are broadly categorized as disease-related under multiple mitochondrial dysfunction syndrome (MMDS), with symptoms indicative of a general failure of the metabolic system. Multiple mitochondrial dysfunction syndrome 1 (MMDS1) arises as a result of the missense mutation in NFU1, an Fe/S cluster scaffold protein, which substitutes a glycine near the Fe/S cluster-binding pocket to a cysteine (p.Gly208Cys). This substitution has been shown to promote protein dimerization such that cluster delivery to NFU1 is blocked, preventing downstream cluster trafficking. However, the possibility of this additional cysteine, located adjacent to the cluster-binding site, serving as an Fe/S cluster ligand has not yet been explored. To fully understand the consequences of this Gly208Cys replacement, complementary substitutions at the Fe/S cluster-binding pocket for native and Gly208Cys NFU1 were made, along with six other variants. Herein, we report the results of an investigation on the effect of these substitutions on both cluster coordination and NFU1 structure and function. The data suggest that the G208C substitution does not contribute to cluster binding. Rather, replacement of the glycine at position 208 changes the oligomerization state as a result of global structural alterations that result in the downstream effects manifest as MMDS1, but does not perturb the coordination chemistry of the Fe-S cluster.
铁硫（Fe/S）簇是存在于众多金属蛋白中的古老辅基，由于其多样但至关重要的功能作用，在所有生命王国中都得以保留。线粒体Fe/S簇传递蛋白特定亚组的基因突变在多重线粒体功能障碍综合征（MMDS）中被广泛归类为与疾病相关，其症状表明代谢系统普遍失灵。多重线粒体功能障碍综合征1（MMDS1）是由NFU1（一种Fe/S簇支架蛋白）中的错义突变引起的，该突变将Fe/S簇结合口袋附近的甘氨酸替换为半胱氨酸（p.Gly208Cys）。已表明这种替换会促进蛋白质二聚化，从而阻断簇向NFU1的传递，阻止下游簇的运输。然而，位于簇结合位点附近的这个额外半胱氨酸作为Fe/S簇配体的可能性尚未得到探索。为了全面了解这种Gly208Cys替换的后果，对天然型和Gly208Cys型NFU1的Fe/S簇结合口袋进行了互补替换，以及其他六个变体。在此，我们报告了关于这些替换对簇配位以及NFU1结构和功能影响的研究结果。数据表明，G208C替换对簇结合没有贡献。相反，208位甘氨酸的替换由于全局结构改变而改变了寡聚化状态，导致下游效应表现为MMDS1，但不会干扰Fe-S簇的配位化学。
