Temperature-Induced Unfolding Pathway of Staphylococcal Enterotoxin B:Insights from Circular Dichroism and Molecular Dynamics Simulation  

金黄色葡萄球菌B型肠毒素热变性过程:源于圆二色光谱及分子动力学模拟的启示

作　　者：LIU Ji ZHANG Shiyu ZENG Yu DENG Yi 刘骥;张诗雨;曾瑜;邓依(西南民族大学青藏高原研究院,四川成都610041;西南民族大学食品科学与技术学院,四川成都610041;五粮液股份有限公司,四川宜宾644000)

机构地区：[1]Institute of Qinghai-Tibetan Plateau,Southwest Minzu University,Chengdu 610041,China [2]College of Food Sciences and Technology,Southwest Minzu University,Chengdu 610041,China [3]Wuliangye Group Co.Ltd.,Yibin 644000,China

出　　处：《食品科学》2024年第18期55-76,共22页Food Science

基　　金：西南民族大学中央高校基本科研业务费专项资金项目(2023NZYQN99)。

摘　　要：In this study,circular dichroism(CD)and molecular dynamics(MD)simulation were used to investigate the thermal unfolding pathway of staphylococcal enterotoxin B(SEB)at temperatures of 298–371 and 298–500 K,and the relationship between the experimental and simulation results were explored.Our computational findings on the secondary structure of SEB showed that at room temperature,the CD spectroscopic results were highly consistent with the MD results.Moreover,under heating conditions,the changing trends of helix,sheet and random coil obtained by CD spectral fitting were highly consistent with those obtained by MD.In order to gain a deeper understanding of the thermal stability mechanism of SEB,the MD trajectories were analyzed in terms of root mean square deviation(RMSD),secondary structure assignment(SSA),radius of gyration(R_(g)),free energy surfaces(FES),solvent-accessible surface area(SASA),hydrogen bonds and salt bridges.The results showed that at low heating temperature,domain Ⅰ without loops(omitting the mobile loop region)mainly relied on hydrophobic interaction to maintain its thermal stability,whereas the thermal stability of domain Ⅱ was mainly controlled by salt bridges and hydrogen bonds.Under high heating temperature conditions,the hydrophobic interactions in domain Ⅰ without loops were destroyed and the secondary structure was almost completely lost,while domain Ⅱ could still rely on salt bridges as molecular staples to barely maintain the stability of the secondary structure.These results help us to understand the thermodynamic and kinetic mechanisms that maintain the thermal stability of SEB at the molecular level,and provide a direction for establishing safer and more effective food sterilization processes.本实验在298~371 K和298~500 K温度范围内,分别利用圆二色(circular dichroism,CD)光谱和分子动力学(molecular dynamics,MD)模拟研究加热过程中金黄色葡萄球菌B型肠毒素(staphylococcal enterotoxin B,SEB)的热变性过程,探索实验与模拟之间的关系。对SEB二级结构研究发现,在室温条件下,CD谱图与MD模拟结果高度一致;在加热条件下,CD谱图拟合出的螺旋、折叠和无规卷曲结构变化趋势与MD模拟结果也高度一致。为深入了解SEB的热稳定机制,对其MD模拟轨迹进行均方根偏差、二级结构含量、回转半径、自由能表面、溶剂可及性表面积以及氢键和盐桥测定分析。MD分析结果表明,在较低的加热温度条件下,不含柔性环的结构域Ⅰ主要依赖疏水相互作用维持其热稳定性,而结构域Ⅱ的热稳定性主要借助于盐桥和氢键。在较高加热温度条件下,不含柔性环的结构域I中疏水相互作用被破坏,其二级结构几乎完全消失。而结构域Ⅱ还能依靠盐桥形成的“分子图钉”在较高加热温度下勉强维系其二级结构稳定性。上述研究结果有助于在分子水平上理解维系SEB热稳定性的热力学和动力学机制,为确立更加安全有效的食品消毒杀菌工艺指明方向。

关 键 词：staphylococcal enterotoxin B circular dichroism molecular dynamics simulations temperature-induced unfolding 

分 类 号：TS201.6[轻工技术与工程—食品科学]