LAUSR

Antifreeze proteins (AFPs) protect organisms from freezing by binding to ice crystals to prevent their growth. Here, we have investigated how the area of an AFP's ice‐binding site (IBS) changes its antifreeze activity. The polyproline type II helical bundle fold of the 9.6‐kDa springtail (Collembola) AFP from Granisotoma rainieri (a primitive arthropod) facilitates changes to both IBS length and width. A one quarter decrease in area reduced activity to less than 10%. A one quarter increase in IBS width, through the addition of a single helix, tripled antifreeze activity. However, increasing IBS length by a similar amount actually reduced activity. Expanding the IBS area can greatly increase antifreeze activity but needs to be evaluated by experimentation on a case‐by‐case basis.