Ghosh Debasish Kumar, Kumar Abhishek, Ranjan Akash
Computational and Functional Genomics Group, Centre for DNA Fingerprinting and Diagnostics Uppal Hyderabad 500039 Telangana India
Graduate Studies, Manipal Academy of Higher Education Manipal Karnataka 576104 India.
RSC Adv. 2020 Mar 13;10(18):10776-10788. doi: 10.1039/c9ra09870d. eCollection 2020 Mar 11.
Mutations cause abnormalities in protein structure, function and oligomerization. Different mutations in the superoxide dismutase 1 (SOD1) protein cause its misfolding, loss of dimerization and aggravate its aggregation in the amyotrophic lateral sclerosis disease. In this study, we report the mechanistic details of how a threonine-to-arginine mutation at the 54 position (T54R) of SOD1 results in destabilization of the dimer interface of SOD1. Using computational and experimental methods, we show that the T54R mutation increases fluctuation of the mutation-harboring loop (R54-loop) of SOD1. Fluctuation of this loop causes steric clashes that involve arginine-54 (R54) and other residues of SOD1, resulting in loss of inter-subunit contacts at the dimer interface. Since the T54 residue-containing loop is necessary for the dimerization of wild-type SOD1, fluctuation of the R54-loop, steric clashes involving R54 and loss of inter-subunit contacts give rise to the loss of SOD1 dimer stability. This correlates to energetically unfavorable tethering of the monomers of SOD1. The outcome is gradual splitting of SOD1 dimers into monomers, thereby exposing the previously buried hydrophobic interface residues to the aqueous environment. This event finally leads to aggregation of SOD1. T54R mutation has no effect in altering the relative positions of copper and zinc ion binding residues of SOD1. The native SOD1 structure is stable, and there is no destabilizing effect at its dimer interface. Overall, our study reveals the intricate mechanism of T54R mutation-associated destabilization of the dimer of the SOD1 protein.
突变会导致蛋白质结构、功能及寡聚化异常。超氧化物歧化酶1（SOD1）蛋白的不同突变会导致其错误折叠、二聚化丧失，并加剧其在肌萎缩侧索硬化症中的聚集。在本研究中，我们报告了SOD1第54位苏氨酸突变为精氨酸（T54R）导致SOD1二聚体界面不稳定的机制细节。通过计算和实验方法，我们表明T54R突变增加了SOD1含突变环（R54环）的波动。该环的波动导致空间冲突，涉及精氨酸54（R54）和SOD1的其他残基，从而导致二聚体界面处亚基间接触丧失。由于含T54残基的环对于野生型SOD1的二聚化是必需的，R54环的波动、涉及R54的空间冲突以及亚基间接触的丧失导致SOD1二聚体稳定性丧失。这与SOD1单体在能量上不利的束缚相关。结果是SOD1二聚体逐渐分裂为单体，从而将先前埋藏的疏水界面残基暴露于水性环境中。这一事件最终导致SOD1聚集。T54R突变在改变SOD1铜离子和锌离子结合残基的相对位置方面没有作用。天然SOD1结构稳定，其在二聚体界面没有去稳定化作用。总体而言，我们的研究揭示了T54R突变相关的SOD1蛋白二聚体不稳定的复杂机制。
