Parody-Morreale A, Murphy K P, Di Cera E, Fall R, DeVries A L, Gill S J
Department of Physical Chemistry, University of Granada, Spain.
Nature. 1988 Jun 23;333(6175):782-3. doi: 10.1038/333782a0.
Certain bacteria promote the formation of ice in super-cooled water by means of ice nucleators which contain a unique protein associated with the cell membrane. Ice nucleators in general are believed to act by mimicking the structure of an ice crystal surface, thus imposing an ice-like arrangement on the water molecules in contact with the nucleating surface and lowering the energy necessary for the initiation of ice formation. Quantitative investigation of the bacterial ice-nucleating process has recently been made possible by the discovery of certain bacteria that shed stable membrane vesicles with ice nucleating activity. The opposite effect, inhibition of ice formation, has been described for a group of glycoproteins found in different fish and insect species. This group of substances, termed antifreeze glycoproteins (AFGPs), promotes the supercooling of water with no appreciable effect on the equilibrium freezing point or melting temperature. Substantial evidence now indicates that AFGPs act by binding to a growing ice crystal and slowing crystal growth. As the ice-nucleating protein surface is believed to have a structure similar to an embryonic ice crystal, AFGPs might be predicted to interact directly with a bacterial ice-nucleating site. We report here that AFGPs from the antarctic fish Dissostichus mawsoni inhibit the ice-nucleating activity of membrane vesicles from the bacterium Erwinia herbicola. The inhibition effect shows saturation at high concentration of AFGP and conforms to a simple binding reaction between the AFGP and the nucleation centre.
某些细菌借助冰核蛋白促进过冷水中冰的形成，这些冰核蛋白含有一种与细胞膜相关的独特蛋白质。一般认为，冰核蛋白的作用是模仿冰晶表面的结构，从而使与成核表面接触的水分子形成类似冰的排列，并降低冰形成起始所需的能量。最近，通过发现某些能释放具有冰核活性的稳定膜泡的细菌，对细菌冰核形成过程的定量研究成为可能。在不同鱼类和昆虫物种中发现的一组糖蛋白具有相反的作用，即抑制冰的形成。这组物质被称为抗冻糖蛋白（AFGP），它能促进水的过冷，而对平衡冰点或熔点没有明显影响。现在有大量证据表明，抗冻糖蛋白通过与生长中的冰晶结合并减缓晶体生长来发挥作用。由于冰核蛋白表面被认为具有与胚胎冰晶相似的结构，可以预测抗冻糖蛋白可能直接与细菌冰核位点相互作用。我们在此报告，南极莫氏 Dissostichus mawsoni 鱼的抗冻糖蛋白可抑制草本欧文氏菌膜泡的冰核活性。抑制作用在高浓度抗冻糖蛋白时表现出饱和，符合抗冻糖蛋白与成核中心之间的简单结合反应。
