Zhang W, Laursen R A
Department of Chemistry, Boston University, MA 02215, USA.
FEBS Lett. 1999 Jul 23;455(3):372-6. doi: 10.1016/s0014-5793(99)00906-0.
Antifreeze polypeptides from fish are generally thought to inhibit ice crystal growth by specific adsorption onto ice surfaces and preventing addition of water molecules to the ice lattice. Recent studies have suggested that this adsorption results from hydrogen bonding through the side chains of polar amino acids as well as hydrophobic interactions between the non-polar domains on the ice-binding side of antifreeze polypeptides and the clathrate-like surfaces of ice. In order to better understand the activity of one of the antifreeze polypeptide families, namely the alpha-helical type I antifreeze polypeptides, four alpha-helical peptides having sequences not directly analogous to those of known antifreeze polypeptides and containing only positively charged and non-polar side chains were synthesized. Two peptides with regularly spaced lysine residues, GAAKAAKAAAAAAAKAAKAAAAAAAKAAKAAGGY-NH2 and GAALKAAKAAAAAALKAAKAAAAAALKAAKAAGGY-NH2, showed antifreeze activity, albeit weaker than seen in natural antifreeze polypeptides, by the criteria of freezing point depression (thermal hysteresis) and ice crystal modification to a hexagonal trapezohedron. Peptides with irregular spacing of Lys residues were completely inactive. Up to now, lysine residues have not been generally associated with antifreeze activity, though they have been implicated in some antifreeze polypeptides. This work also shows that lysine residues in themselves, when properly positioned on an alpha-helical polyalanine scaffold, have all the requisite properties needed for such an activity.
一般认为，鱼类的抗冻多肽通过特异性吸附在冰表面并阻止水分子添加到冰晶格中来抑制冰晶生长。最近的研究表明，这种吸附是由极性氨基酸侧链之间的氢键以及抗冻多肽冰结合侧的非极性结构域与冰的笼状表面之间的疏水相互作用导致的。为了更好地理解其中一个抗冻多肽家族，即α-螺旋I型抗冻多肽的活性，合成了四种α-螺旋肽，其序列与已知抗冻多肽的序列没有直接相似性，且仅包含带正电荷和非极性的侧链。两种具有规则间隔赖氨酸残基的肽，GAAKAAKAAAAAAAKAAKAAAAAAAKAAKAAGGY-NH2和GAALKAAKAAAAAALKAAKAAAAAALKAAKAAGGY-NH2，通过冰点降低（热滞）和将冰晶形态改变为六方偏方面体的标准显示出抗冻活性，尽管比天然抗冻多肽中的活性弱。赖氨酸残基间隔不规则的肽完全没有活性。到目前为止，赖氨酸残基一般与抗冻活性无关，尽管它们在一些抗冻多肽中有所涉及。这项工作还表明，当赖氨酸残基适当地定位在α-螺旋聚丙氨酸支架上时，它们具有这种活性所需的所有必要特性。
