Lu Weina, Jiang Zhuo, Lin Qi, Yang Zhecheng, Liu Yanli, Bi Wenhui, You Zhengying, Jiang Caiying, Sheng Qing, Nie Zuoming
College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Hangzhou, 310018, China.
Protein J. 2025 Jul 18. doi: 10.1007/s10930-025-10280-x.
Superoxide dismutase (SOD) is found in a variety of organisms, including animals, plants, and microorganisms, and is widely used in medicine, food, and cosmetics. In this study, a novel heat-resistant SOD from Rhodothermus sp. XMH10 (RhSOD) has been found to have no loss of activity at 80 °C and exhibit high thermal stability across a temperature range from 20 °C to 80 °C. Unlike other reported SODs, RhSOD was found to have a unique small α-helix tail at the C-terminus, consisting of 11 amino acid residues. The absence of the C-terminal α-helix tail of RhSOD was shown to reduce its activity and thermal stability at 80 °C, suggesting that the C-terminal α-helix tail is crucial for the high thermal stability of RhSOD. Furthermore, the fusion of the C-terminal α-helix tail to the C-terminus of a thermophilic SOD from Anoxybacillus caldiproteolyticus (AcSOD) enhances its thermal stability at 70 °C and 80 °C. Circular dichroism (CD) spectral analysis further indicated that the C-terminal α-helix tail could improve the α-helix content, thus enhancing the structural stability of AcSOD. Thus, a novel C-terminal α-helix tail was firstly discovered, which could confer significant thermal stability to host proteins. This finding provides a new theoretical basis for the study of protein thermostability mechanism.
超氧化物歧化酶（SOD）存在于包括动物、植物和微生物在内的多种生物体中，并且广泛应用于医学、食品和化妆品领域。在本研究中，已发现来自嗜热栖热菌属XMH10菌株（RhSOD）的一种新型耐热SOD在80℃时活性无损失，并且在20℃至80℃的温度范围内表现出高热稳定性。与其他已报道的SOD不同，发现RhSOD在C末端有一个独特的小α螺旋尾巴，由11个氨基酸残基组成。结果表明，RhSOD缺失C末端α螺旋尾巴会降低其在80℃时的活性和热稳定性，这表明C末端α螺旋尾巴对于RhSOD的高热稳定性至关重要。此外，将C末端α螺旋尾巴融合到嗜热解蛋白酶嗜热栖芽孢杆菌（AcSOD）的嗜热SOD的C末端，可提高其在70℃和80℃时的热稳定性。圆二色性（CD）光谱分析进一步表明，C末端α螺旋尾巴可提高α螺旋含量，从而增强AcSOD的结构稳定性。因此，首次发现了一种新型的C末端α螺旋尾巴，它可以赋予宿主蛋白显著的热稳定性。这一发现为蛋白质热稳定性机制的研究提供了新的理论基础。
