Structure-function relationships in an antifreeze polypeptide. The role of charged amino acids

• Published in: The Journal of biological chemistry Vol. 268; no. 22; pp. 16396 - 16400
• Main Authors: Wen, D, Laursen, R A
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Biochemistry and Molecular Biology 05.08.1993
• Subjects: Amino Acid Sequence; Amino Acids - chemistry; Analytical, structural and metabolic biochemistry; Antifreeze Proteins; Biological and medical sciences; Electrochemistry; Freezing; Fundamental and applied biological sciences. Psychology; Glycoproteins - chemistry; Glycoproteins - metabolism; Miscellaneous; Molecular Sequence Data; Proteins; Structure-Activity Relationship; Thermodynamics; Electric charge; Structure activity relation; Antifreeze protein; Analog
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(19)85433-9

Several analogs of an alanine-rich alpha-helical antifreeze polypeptide were synthesized and studied to evaluate the role of charged amino acids on structure and activity. alpha-Helix content and thermal stability were assessed by circular dichroism spectrometry and antifreeze activity by freezing point depression (thermal hysteresis) and ice crystal growth rate measurements. Rearrangement, deletion and replacement of charged amino acids resulted in reduced helicity and antifreeze activity in some cases, but the effects were not dramatic. We conclude that the i+4 ion pair Lys18/Glu22 helps to stabilize the alpha-helix but is not absolutely essential for activity. NH2-terminal Asp does not contribute significantly to helix stability or activity, but the COOH terminus is sensitive to modification, since replacement of Arg37 can lead to reduced helix content and activity. In general, factors which reduce alpha-helix content also reduce antifreeze activity.