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Artificial antifreeze polypeptides: α‐helical peptides with KAAK motifs have antifreeze and ice crystal morphology modifying properties
Author(s) -
Zhang Wei,
Laursen Richard A.
Publication year - 1999
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(99)00906-0
Subject(s) - antifreeze protein , antifreeze , ice crystals , chemistry , polar , amino acid , freezing point , peptide , psychrophile , crystallography , stereochemistry , biochemistry , organic chemistry , thermodynamics , physics , astronomy , optics , enzyme
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 α‐helical type I antifreeze polypeptides, four α‐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, GAAKAAKKAAKKAAKAAGGY‐NH 2 and GAALKAAKLKAAKLKAAKAAGGY‐NH 2 , 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 α‐helical polyalanine scaffold, have all the requisite properties needed for such an activity.