Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, College of Fisheries and Life Science, Shanghai Ocean University, Shanghai 201306, China.
Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
Nat Commun. 2016 Oct 4;7:12987. doi: 10.1038/ncomms12987.
The mechanisms by which the eggs of the Antarctic notothenioid fishes avoid freezing are not fully understood. Zona pellucida proteins (ZPs) are constituents of the chorion which forms a protective matrix surrounding the egg. Here we report occurrence of freezing temperature-related gene expansion and acquisition of unusual ice melting-promoting (IMP) activity in a family of Antarctic notothenioid ZPs (AnnotoZPs). Members of AnnotoZPs are shown to bind with ice and non-colligatively depress the melting point of a solution in a range of 0.26 to 0.65 °C at a moderate concentration. Eggs of zebrafishes expressing an AnnotoZP transgene show improved melting point depression and enhanced survival in freezing conditions. Mutational analyses in a representative AnnotoZP indicate the ZP domain and patches of acidic residues are essential structures for the IMP activity. AnnotoZPs, therefore, represent a group of macromolecules that prevent freezing by a unique ZP-ice interaction mechanism distinct from the known antifreeze proteins.
南极鳕鱼的卵子避免冻结的机制尚未完全阐明。卵透明带蛋白（ZP）是构成围绕卵子的保护基质的卵壳的组成部分。在这里，我们报告了在南极鳕鱼的 ZP 家族（AnnotoZPs）中发生的与冷冻温度相关的基因扩展和获得不寻常的冰融化促进（IMP）活性。AnnotoZPs 成员被证明与冰结合，并在中等浓度下在 0.26 至 0.65°C 的范围内非缔合地降低溶液的熔点。表达 AnnotoZP 转基因的斑马鱼的卵子显示出改善的熔点降低和在冷冻条件下增强的存活能力。在代表性的 AnnotoZP 中的突变分析表明，ZP 结构域和酸性残基补丁是 IMP 活性的必需结构。因此，AnnotoZPs 代表了一组通过独特的 ZP-冰相互作用机制防止冻结的大分子，该机制与已知的抗冻蛋白不同。
