Ice-binding proteins from enoki and shiitake mushrooms

Fungi have developed a variety of mechanisms for tolerating cold, including production of proteins that bind to ice, as shown by their ability to slightly lower the freezing point. At present, only one of these proteins, from the snow mold Typhula ishikariensis, and partial transcripts of a similar protein from shiitake mushroom, Lentinula edodes, have been identified. Here, we report the full sequences of ice-binding proteins from shiitake and another mushroom, the cold-adapted Flammulina populicola (enoki mushroom), and show that the recombinant proteins have ice-binding activity. The three proteins share 50-55% identities and are similar to other ice-binding proteins recently identified in ice bacteria and sea ice diatoms. The possibility that ice-binding protein genes have spread among these phyla by horizontal transfer is discussed.