Why would a protein need to bind to ice?
Well, ice can be a significant problem for cells, and therefore for the organisms that are made from those cells. Crystals generally have sharp edges that can pierce membranes; they also render immobile the flow of small molecules and proteins in the cell. The solution to this problem – faced by many creatures that live in cold climates – is to bind any crystals of ice before they have a chance to grow larger. Even if the crystalisation process cannot be stopped completely, the ice particles can be made more rounded and less damaging to the membrane. How does it bind to ice? Ice is, of course, just frozen water – and all proteins have some interaction with their solvent. However, the water molecules in ice are arranged in a regular array (a crystal), so that the best way to bind is to have regular spacing of surface residues. In other words, there is a pattern to the groups on the outside of these proteins which mirrors the structure of the ice. This is clearest in those proteins with
