Espeche Lucía D, Sewell Karl Ellioth, Castro Ignacio H, Capece Luciana, Pignataro María Florencia, Dain Liliana, Santos Javier
Departamento de Diagnóstico Genético, Centro Nacional de Genética Médica "Dr. Eduardo E. Castilla" A.N.L.I.S., Av. Las Heras 2670, C1425ASQ, C.A.B.A, Argentina.
Instituto de Biociencias, Biotecnología y Biología Traslacional (iB(3)), Departamento de Fisiología y Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires. Intendente Güiraldes 2160, Ciudad Universitaria, C1428EGA, Buenos Aires, Argentina.
Arch Biochem Biophys. 2022 Jan 15;715:109086. doi: 10.1016/j.abb.2021.109086. Epub 2021 Nov 19.
In humans, the loss of frataxin results in Friedreich's Ataxia, a neurodegenerative disease, in which a deficit in the iron-sulfur cluster assembly is observed. In this work, we analyzed three frataxin variants in which one tryptophan was replaced by a glycine: W155G, W168G and W173G. As expected, given its localization in the assembly site, W155G was not able to activate the desulfurase activity of the supercomplex for iron-sulfur cluster assembly. In turn, W168G, which was significantly more unstable than W155G, was fully active. W173G, which was highly unstable as W168G, showed a significantly decreased activity, only slightly higher than W155G. As W168G and W173G were highly sensitive to proteolysis, we investigated the protein motions by molecular dynamic simulations. We observed that W173G may display altered motions at the Trp155 site. Furthermore, we revealed a H-bond network in which Trp155 takes part, involving residues Gln148, Asn151, Gln153 and Arg165. We suggest that this motion modulation that specifically alters the population of different Trp155 rotamers can be directly transferred to the assembly site, altering the dynamics of the ISCU His137 key residue. This hypothesis was also contrasted by means of molecular dynamic simulations of frataxin in the context of the complete supercomplex. We propose that the supercomplex requires very definite motions of Trp155 to consolidate the assembly site.
在人类中，铁调素的缺失会导致弗里德赖希共济失调症，这是一种神经退行性疾病，在该疾病中可观察到铁硫簇组装存在缺陷。在这项研究中，我们分析了三种铁调素变体，其中一个色氨酸被甘氨酸取代：W155G、W168G和W173G。正如预期的那样，鉴于其在组装位点的定位，W155G无法激活用于铁硫簇组装的超复合物的脱硫酶活性。反过来，比W155G明显更不稳定的W168G却具有完全活性。与W168G一样高度不稳定的W173G，其活性显著降低，仅略高于W155G。由于W168G和W173G对蛋白水解高度敏感，我们通过分子动力学模拟研究了蛋白质的运动。我们观察到W173G可能在色氨酸155位点表现出改变的运动。此外，我们揭示了一个色氨酸155参与其中的氢键网络，涉及谷氨酰胺148、天冬酰胺151、谷氨酰胺153和精氨酸165。我们认为，这种特异性改变不同色氨酸155旋转异构体数量的运动调节可直接传递到组装位点，改变铁硫簇组装支架蛋白（ISCU）组氨酸137关键残基的动力学。在完整超复合物的背景下对铁调素进行的分子动力学模拟也验证了这一假设。我们提出，超复合物需要色氨酸155非常明确的运动来巩固组装位点。
