College of Vocational and Technical Education, Yunnan Normal University, Kunming, Yunnan, China.
Instituto de Física, Universidade de São Paulo, São Paulo, Brazil.
Colloids Surf B Biointerfaces. 2023 Oct;230:113490. doi: 10.1016/j.colsurfb.2023.113490. Epub 2023 Aug 3.
In order to highlight the role of hydrophobic interactions in the molten globule (MG) state of globular protein modulated by surfactants, the interactions of bovine α-lactalbumin (α-LA) with alkyl trimethylammonium bromides (CTAB, n = 10, 12, 14, and 16) have been studied by experimental and theoretical techniques. Isothermal titration calorimetry (ITC) showed that the enthalpy changes (ΔH) and area of the enthalpogram increased with increasing the chain length of CTAB. The result of fluorescence, circular dichroism (CD) and H nuclear magnetic resonance (NMR) spectrum suggested that C10TAB and C12TAB unfolded α-LA partially, C14TAB reconstructed protein with a native-like secondary structure content, and C16TAB induced an MG state α-LA. The SAXS results confirmed that the tertiary structure of α-LA was disrupted by C16TAB forming an MG state complex with a micelle-like structure even at the surfactants concentrations below CMC. As indicated by MD results, the β-domain and unstructured region(s) were involved in the MG state α-LA modulated by CTAB. This work not only provides molecular insights into the role of hydrophobic interactions in the MG state of a globular protein but also helps understand the mechanism of preparing α-LA based biomacromolecule modulated by hydrophobic interactions.
为了突出疏水相互作用在表面活性剂调节的球状蛋白变性状态（MG 状态）中的作用，通过实验和理论技术研究了牛α-乳白蛋白（α-LA）与烷基三甲基溴化铵（CTAB，n=10、12、14 和 16）的相互作用。等温滴定量热法（ITC）表明，焓变（ΔH）和焓图面积随 CTAB 链长的增加而增加。荧光、圆二色性（CD）和 H 核磁共振（NMR）谱的结果表明，C10TAB 和 C12TAB 部分展开了α-LA，C14TAB 用类似天然的二级结构含量重建了蛋白质，而 C16TAB 诱导了 MG 状态的α-LA。小角 X 射线散射（SAXS）结果证实，α-LA 的三级结构被 C16TAB 破坏，即使在低于 CMC 的表面活性剂浓度下，也形成了具有胶束样结构的 MG 状态复合物。正如 MD 结果所示，β 结构域和无规卷曲区域（s）参与了 CTAB 调节的 MG 状态的α-LA。这项工作不仅提供了分子见解，说明了疏水相互作用在球状蛋白的 MG 状态中的作用，还有助于理解基于疏水相互作用制备α-LA 调节的生物大分子的机制。
