How Do Antifreeze Proteins Help Antarctic Fish Survive the Cold?

[bard]

Anyone know the answer to this ridiculous problem

Antarctic notothenioid fish avoid freezing in their perpetually icy environment because of an antifreeze protein that circulates in their blood. This evolutionary adaptation has allowed these fish to rise to dominance in the freezing southern ocean. It is said that all proteins function by binding to other molecules. To what ligand do you suppose antifreeze proteins bind to keep the fish from freezing.? Or do you think this might be an example of a protein that functions in the absence of any molecular interaction?

Anyone have any suggestions, thanks

 

[Jikx]

I would have to guess... the ligand would be ice crystals to stop them from growing.

 

[FZ+]

If there is a ligand, then I suppose it would be water. Some chemical functioning in the absence of any interaction sounds kinda fishy to me... Pun intended. But biology isn't my thing.

 

[iansmith]

I would have to guess... the ligand would be ice crystals to stop them from growing.

You are right. The protein binds to tiny ice crystal and prevent the growth of these crystals.

But in more technical terms

These compounds allow the fish to survive in subzero ice-laden polar oceans by kinetically depressing the temperature at which ice grows in a noncolligative manner.

http://www.ncbi.nlm.nih.gov/entrez/...ve&db=pubmed&dopt=Abstract&list_uids=12653993

More info
http://www.ncbi.nlm.nih.gov/entrez/...rm=Antarctic+Notothenioids+antifreeze+protein

 

[Moonbear]

It seems the question has already been answered. The choice of the word "ligand" seems odd in this context. I usually think of ligand as a molecule binding to a receptor, not just any molecular interaction. I wouldn't consider water to be a "ligand" in the true sense of the word.

 

[DocToxyn]

It seems the question has already been answered. The choice of the word "ligand" seems odd in this context. I usually think of ligand as a molecule binding to a receptor, not just any molecular interaction. I wouldn't consider water to be a "ligand" in the true sense of the word.

I agree, in most cases the ligand elicits some sort of reaction in the protein it is binding to, i.e., conformational change, translocation, channel activation, etc. In this case it appears that active groups, the long chain amino acids are functionally exposed prior to exposure to ice and ready to interact with the forming edges of ice crystals, so it's not necessarily reacting but simply inhibiting.