Nasiri Parto, Ghahramani Maryam, Tavaf Zohreh, Niazi Ali, Moosavi-Movahedi Ali Akbar, Kurganov Boris I, Yousefi Reza
Protein Chemistry Laboratory (PCL), Department of Biology, College of Sciences, Shiraz University, Shiraz, Iran.
Institute of Biotechnology, Shiraz University, Shiraz, Iran.
Biochimie. 2021 Nov;190:36-49. doi: 10.1016/j.biochi.2021.06.019. Epub 2021 Jul 5.
In human αB-crystallin or HspB5, the substitution of arginine residue at position 157 with histidine has been reported to cause cardiomyopathy. In this study, the impact of R157H mutation on the structure, stability and functional properties of human αB-crystallin was investigated using a variety of spectroscopic techniques and microscopic analyses. Our spectroscopic analyses revealed that this mutation has a negligible impact on the secondary and tertiary structures of HspB5 but its quaternary structure underwent fundamental changes. Although the chemical stability of the mutant protein remained largely unchanged, the differential scanning calorimetry (DSC) measurement suggested that its thermal stability was reduced. As examined with transmission electron microscopy, αB-crystallin and its mutant indicated a similar tendency for the amyloid fibril formation under thermochemical stress. Dynamic light scattering (DLS) analysis suggested important changes in the quaternary (oligomeric) structures of the mutant protein as compared with the native protein counterpart. Also, the mutant protein indicated an improved chaperone-like activity under in vitro assessment. In a pH-dependent manner, the side chains of arginine and histidine have different capabilities for establishing hydrogen bonds and electrostatic interaction (salt bridge) and this variation may be sufficient to produce the larger changes that ultimately alter the interaction of this protein with other target proteins. Overall, the pathogenic contribution of this mutation in cardiomyopathy can be explained by its role in quaternary structure/stability alteration of the mutated protein.
据报道，在人类αB-晶状体蛋白或热休克蛋白B5（HspB5）中，第157位精氨酸残基被组氨酸取代会导致心肌病。在本研究中，使用多种光谱技术和显微镜分析方法，研究了R157H突变对人类αB-晶状体蛋白的结构、稳定性和功能特性的影响。我们的光谱分析表明，这种突变对HspB5的二级和三级结构影响可忽略不计，但其四级结构发生了根本性变化。虽然突变蛋白的化学稳定性基本保持不变，但差示扫描量热法（DSC）测量表明其热稳定性降低。通过透射电子显微镜检查发现，αB-晶状体蛋白及其突变体在热化学应激下形成淀粉样纤维的趋势相似。动态光散射（DLS）分析表明，与天然蛋白相比，突变蛋白的四级（寡聚）结构发生了重要变化。此外，在体外评估中，突变蛋白表现出增强的伴侣样活性。精氨酸和组氨酸的侧链在建立氢键和静电相互作用（盐桥）方面具有不同的pH依赖性能力，这种差异可能足以产生更大的变化，最终改变该蛋白与其他靶蛋白的相互作用。总体而言，这种突变在心肌病中的致病作用可以通过其在突变蛋白四级结构/稳定性改变中的作用来解释。
