Ice-binding site of surface-bound type III antifreeze protein partially decoupled from water.
Ice-binding site of surface-bound type III antifreeze protein partially decoupled from water.
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DOI：
10.1039/c8cp03382j
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发表时间：
2018-10
期刊：
影响因子：
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通讯作者：
D. Verreault;S. Alamdari;Steven Joop Roeters;R. Pandey;J. Pfaendtner;T. Weidner
中科院分区：
文献类型：
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作者：
D. Verreault;S. Alamdari;Steven Joop Roeters;R. Pandey;J. Pfaendtner;T. Weidner
Ⅲ型抗冻蛋白（AFP Ⅲ）是一类由多种生物体产生的抗冻蛋白。除了通过其冰结合位点（IBS）限制冰生长的能力外，AFP III还显示出对疏水表面（如空气-水界面）具有很大的倾向。然而，目前尚不清楚AFP III是否以特定方向吸附以及疏水相互作用如何影响IBS。IBS的可及性及其与水的相互作用的分子见解对于理解AFP III在体内的作用是重要的，而且对于它们作为防冻剂用于除冰、冷冻食品储存以及长期血液和器官冷冻保存的应用也是重要的。在这里，吸附在空气-水界面的鱼AFP III的取向已经研究了使用分子动力学（MD）模拟和振动和频发生（SFG）光谱与光谱计算的组合。SFG/MD分析表明，当AFP III吸附在空气-水界面上时，它主要保持其天然状态，并且相对于表面法线以120°的倾斜角取向。我们发现，IBS是只有部分溶剂化，离开金字塔形的冰平面结合域暴露于气相。这些发现表明，与疏水界面的相互作用（例如，细胞膜、聚合物）可导致IBS与水的部分解偶联，并在一定程度上导致AFPIII防冻活性的丧失。
Type III antifreeze proteins (AFP III) have been widely recognized as one class of ice-binding proteins produced by several biological organisms to withstand freezing conditions. Besides their ability to restrict ice growth through their ice-binding site (IBS), AFP III have also been shown to possess a great propensity for hydrophobic surfaces such as the air-water interface. Yet, it is not known whether AFP III adsorb with a specific orientation and how hydrophobic interactions affect the IBS. Molecular insights on the accessibility of the IBS and its interactions with water are important for understanding AFP III action in vivo but also for their application as ice-inhibiting agents for deicing, frozen food storage, as well as for long-term blood and organ cryo-preservation. Here, the orientation of fish AFP III adsorbed at the air-water interface has been studied using a combination of molecular dynamics (MD) simulations and vibrational sum-frequency generation (SFG) spectroscopy together with spectral calculations. The SFG/MD analysis indicated that when AFP III adsorbs at the air-water interface, it mostly retains its native state and orients with a tilt angle of 120° with respect to the surface normal. We found that the IBS is only partially solvated, leaving the pyramidal ice plane binding domain exposed to the vapor phase. These findings suggest that interactions with hydrophobic interfaces (e.g., cell membranes, polymers) could lead to the partial decoupling of the IBS from water and, to some extent, to a loss of AFP III antifreezing activity.