Department of Bioinformatics and Telemedicine, Jagiellonian University, Medical College, Lazarza 16, 31-530, Krakow, Poland.
Chair of Medical Biochemistry, Jagiellonian University, Medical College, Kopernika 7, 31-034, Krakow, Poland.
Biochimie. 2018 Jan;144:74-84. doi: 10.1016/j.biochi.2017.10.011. Epub 2017 Oct 17.
Proteins whose presence prevents water from freezing in living organisms at temperatures below 0 °C are referred to as antifreeze proteins. This group includes molecules of varying size (from 30 to over 300 aa) and variable secondary/supersecondary conformation. Some of these proteins also contain peculiar structural motifs called solenoids. We have applied the fuzzy oil drop model in the analysis of four categories of antifreeze proteins: 1 - very small proteins, i.e. helical peptides (below 40 aa); 2 - small globular proteins (40-100 aa); 3 - large globular proteins (>100 aa) and 4 - proteins containing solenoids. The FOD model suggests a mechanism by which antifreeze proteins prevent freezing. In accordance with this theory, the presence of the protein itself produces an ordering of water molecules which counteracts the formation of ice crystals. This conclusion is supported by analysis of the ordering of hydrophobic and hydrophilic residues in antifreeze proteins, revealing significant variability - from perfect adherence to the fuzzy oil drop model through structures which lack a clearly defined hydrophobic core, all the way to linear arrangement of alternating local minima and maxima propagating along the principal axis of the solenoid (much like in amyloids). The presented model - alternative with respect to the ice docking model - explains the antifreeze properties of compounds such as saccharides and fatty acids. The fuzzy oil drop model also enables differentiation between amyloids and antifreeze proteins.
在 0°C 以下的温度下，能够防止生物体内的水结冰的蛋白质被称为抗冻蛋白。这组蛋白质包含了大小不同（30 到 300 多个氨基酸）和可变的二级/超二级构象的分子。其中一些蛋白质还包含了奇特的结构模体，称为螺旋。我们已经将模糊油滴模型应用于四类抗冻蛋白的分析：1-非常小的蛋白质，即螺旋肽（小于 40 个氨基酸）；2-小的球形蛋白质（40-100 个氨基酸）；3-大的球形蛋白质（大于 100 个氨基酸）和 4-包含螺旋的蛋白质。FOD 模型提出了抗冻蛋白防止结冰的机制。根据这一理论，蛋白质本身的存在会导致水分子的有序排列，从而抵消冰晶的形成。这一结论得到了对抗冻蛋白中疏水性和亲水性残基有序性分析的支持，揭示了显著的可变性——从完全符合模糊油滴模型到缺乏明确疏水核心的结构，再到沿螺旋的主轴交替局部最小值和最大值的线性排列（非常类似于淀粉样蛋白）。所提出的模型——与冰对接模型不同——解释了糖和脂肪酸等化合物的抗冻性质。模糊油滴模型还能够区分淀粉样蛋白和抗冻蛋白。
