Structure-function relationships in a winter flounder antifreeze polypeptide. I. Stabilization of an alpha-helical antifreeze polypeptide by charged-group and hydrophobic interactions.

摘要: Abstract The major antifreeze polypeptide (AFP) from winter flounder (37 amino acid residues) is a single alpha-helix. Aspartic and arginine are found, respectively, at the carboxyl-termini. These charged acids ideally located for stabilizing alpha-helical conformation of this AFP by means charge-dipole interaction (Shoemaker, K. R., Kim, P.S., York, E.J., Stewart, J. M., Baldwin, R. L. (1987) Nature 326, 563-567). In order to understand these other molecular interactions that maintain structure, we have carried out chemical synthesis analogs evaluated their conformations circular dichroism spectroscopy. We synthesized entire molecule (37-mer) six COOH-terminal peptide fragments (36-, 33-, 27-, 26-, 16-, 15-mers). Peptides containing acidic NH2-terminal residues displayed greater helix formation thermal stability compared those peptides similar size, but with neutral residues. Helix was maximum above pH 9.2. also pH-dependent sensitivity changes in ionic strength. reduced presence acetonitrile. conclude most likely stabilized by: between terminal dipole, charge Lys18 Glu22 (either salt bridge or hydrogen bond), hydrophobic interactions.