Discovery of antifreeze proteins

It has been 40 years since Scholander and colleagues first travelled to Labrador to resolve what was thought to be a simple question: how do marine teleosts avoid freezing in icy seawater at temperatures (−1.8°C) approximately 1°C below the freezing point of their body fluids (−0.7°C) (Scholander et al, 1957)? They made two important observations as a result of their expeditions. The first was that some fish exist in a super cooled state; that is, at temperatures below their freezing points. However, if these fish are brought into contact with ice, they immediately freeze and die. The combination of super cooling and ice contact is lethal. The second observation was that other fish are able to survive at very low temperatures because their blood has the same freezing point as seawater. The blood solute responsible for lowering the freezing point was named ‘antifreeze’ by these pioneering researchers, but they were unable to determine its nature (Gordon, Andur & Scholander, 1962).

It took almost 10 years before the nature of these freeze-protecting plasma solutes was discovered by DeVries and Wohlschlag (1969) and characterised by DeVries, Komatsu and Feeney (1970). It is now known that they are polypeptides or glycopeptides, which are primarily synthesised in the liver and secreted into the blood. Still collectively termed ‘antifreeze’, these proteins are 200–300 times better at lowering the freezing point than would be expected on the basis of the number of antifreeze molecules present in solution (colligative properties) alone. Thus, fish have evolved a mechanism to reduce the freezing point of their body fluids without changing the osmotic properties of these fluids appreciably.