A cold season is coming near and we begin to think of keeping our body warm. We are able to keep off the coldness by heavily clothed or by heating. However, other animals cannot behave like us. Especially, fishes living in icy oceans near the polar regions where the temperature of sea water becomes under zero degree in winter, are, owing to the fact that they are poikilotherm, exposed to the risk of freezing. How, on earth, do the fishes protect their lives under such severe conditions?

"Necessity is the mother of invention" for fishes whose lives are in peril

Pure water freezes at zero degree; the freezing point of the blood of fishes containing salt and other substances is reduced to -0.8 degrees. This principle is applied to antifreezing fluids in automobiles: if a certain substance is added to cooling water for engine, the freezing point of the water is greatly reduced and the water does not freeze even in a very cold season.
Sea water, on the other hand, containing substances such as salt just as the blood of fishes, freezes also at a temperature below zero degree. However, since the concentration of salts in sea water is higher than in the blood of fishes, the freezing point of sea water becomes -1.9 degrees. The temperature of sea water with ices is then the same as the freezing point or -1.9 degrees. Therefore, if the fishes under such conditions have no mechanism for lowering further the freezing point of their blood by more than 1 degree, their lives become in peril. Then the fishes, driven by necessity for the protection of their lives, have developed biological antifreezes called antifreeze proteins. These proteins are produced in the liver and sent out to circulate with blood for lowering the freezing point of the blood to -2.2 degrees, which is low enough to save the fishes from freezing.
A flounder is careful enough as to produce antifreeze proteins just before the cold season sets in; a cod synthesizes ones in response to the coming of the cold season. An ocean pout in the Antarctic ocean where the temperature of sea water is always very low naturally continues to produce antifreeze proteins all year. It is a wonder that the fishes living under similar conditions have developed independently proteins having the same function in spite of the fact that each species acts as its own way to produce antifreeze proteins and the sequence of amino acids of the antifreeze proteins is different to each other.

There is profound significance in the similarities between melodies of proteins

By the way, what characteristics are there in the melody of such antifreeze proteins? It is the repetition of a melody piece with a fast rhythm, as can be seen from the score shown as an example. When a cold season comes, fishes living in a cold ocean play the melody in their body to synthesize antifreezing proteins and protect themselves from the coldness.
In fact, the melody has similar effects on us. In other words, to hum the tune is "the trick for self-heating when it is cold". If you feel coldness, try to sing the melody in quick tempo while chafing hands together. You surely feel yourself becoming warm. Although human beings do not have the antifreeze proteins, the melody acts on proteins with similar melody pieces and brings us similar effects.
It is to be noted, however, that the protein music should be treated cautiously. If you hum the melody when unnecessary, for example when you do not feel coldness, you may become feverish as a result of ill effects of the melody. This can be understood by the fact that a protein of a plasmodium contains the identical melody pieces to that of the antifreeze protein although the sequence of amino acids is different to each other. If the function of the melody to make us warm is appropriate in a coldness, the same function makes us feverish in a hotness.
The similarity of melodies between proteins which are quite different to each other is called "musical homologies" by Dr. Sternheimer, who explains the significance as follows: "Based upon the musical homologies, one may be able to predict the functions of a protein whose functions are still unknown. For example, since the antifreeze protein and a protein of a plasmodium have melody pieces in common as explained above, we know that these two proteins have a common function."
As the example shows us, the fact that different proteins have the same melody pieces is not a simple coincidence but very significant. We can then think of many applications of the protein music based on the fact.