Cryoprotectants and ice-binding proteins

Abstract

Some bacteria have developed a variety of strategies to survive and colonize extremely cold environments such as the Antarctic and the Arctic. In these frozen environments, bacteria are exposed to conditions that necessitate the partial removal of water from the intracellular space in order to maintain the structure and function of the cell. To avoid the dehydration condition under frozen environments, bacteria can accumulate small compounds, i.e. Glucose, trehalose, etc., for keeping the unfrozen conditions. Also, some bacteria can produce some ice crystal-controlling materials into the intracellular or extracellular space. The ice crystal-controlling materials are ice-nucleating proteins, anti-nucleating materials, and antifreeze proteins. Among these three compounds, ice-nucleating proteins can facilitate the ice-nucleating activity at temperatures more than -3 °C. Also, antinucleating materials can inhibit ice-nucleating activity, thereby facilitating the supercooling temperature. Antifreeze proteins can inhibit ice crystal growth by binding with the surface of ice crystal. The production of these materials can diminish the fear of physical action by ice crystals in the intra- or extracellular space. In this chapter, the origin, structure, and functions of the ice crystalcontrolling materials are mentioned.