Department of Chemistry , 315 South 1400 East , The University of Utah , Salt Lake City , Utah 84112-0580 , United States.
Department of Chemistry and Biochemistry , University of California, San Diego , 9500 Gilman Drive , La Jolla , California 92093 , United States.
J Am Chem Soc. 2018 Apr 11;140(14):4905-4912. doi: 10.1021/jacs.8b01246. Epub 2018 Apr 2.
Cold-adapted organisms produce antifreeze and ice-nucleating proteins to prevent and promote ice formation. The crystal structure of hyperactive bacterial antifreeze protein (AFP) MpAFP suggests that this protein binds ice through an anchored clathrate motif. It is not known whether other hyperactive AFPs and ice-nucleating proteins (INPs) use the same motif to recognize or nucleate ice. Here we use molecular simulations to elucidate the ice-binding motifs of hyperactive insect AFPs and a model INP of Pseudomonas syringae. We find that insect AFPs recognize ice through anchored clathrate motifs distinct from that of MpAFP. By performing simulations of ice nucleation by PsINP, we identify two distinct ice-binding sites on opposite sides of the β-helix. The ice-nucleating sequences identified in the simulations agree with those previously proposed for the closely related INP of Pseudomonas borealis based on the structure of the protein. The simulations indicate that these sites have comparable ice-nucleating efficiency, but distinct binding motifs, controlled by the amino acid sequence: one is an anchored clathrate and the other ice-like. We conclude that anchored clathrate and ice-like motifs can be equally effective for binding proteins to ice and promoting ice nucleation.
适应寒冷的生物体产生抗冻蛋白和冰核蛋白，以防止和促进冰的形成。超活性细菌抗冻蛋白（AFP）MpAFP 的晶体结构表明，该蛋白通过锚定的笼形水合物基序结合冰。目前尚不清楚其他超活性 AFP 和冰核蛋白（INP）是否使用相同的基序来识别或成核冰。在这里，我们使用分子模拟来阐明超活性昆虫 AFP 和假单胞菌的模型 INP 的冰结合基序。我们发现昆虫 AFP 通过与 MpAFP 不同的锚定笼形水合物基序识别冰。通过模拟 PsINP 的冰核形成，我们在β-螺旋的相对两侧鉴定出两个不同的冰结合位点。模拟中确定的冰核序列与基于蛋白质结构的近缘 INP 假单胞菌的冰核序列一致。模拟表明，这些位点具有可比的冰核形成效率，但结合基序不同，由氨基酸序列控制：一个是锚定的笼形水合物，另一个是冰状。我们得出结论，锚定的笼形水合物和冰状基序都可以有效地将蛋白质结合到冰上并促进冰核形成。
