Purification and characterisation of an antifreeze protein from Forsythia suspensa (L.)

Recrystallisation inhibition (RI) activity has been isolated from cold-acclimated Forsythia suspensa bark and leaves, which is stable when boiled, and not sensitive to reducing agents. The antifreeze activity has been purified to a single 20 kDa protein, using anion exchange, hydroxyapatite chromatography, and gel filtration. The protein is abundant in forsythia bark with 0.5 μg pure protein obtained from 35 g bark. RI activity is seen with as little as 6 μg ml−1 protein. Sequence homology was seen with dehydrins, and forsythia AFP contains the Y-segment, a conserved region found in many dehydrins.