Purification and composition of an ice nucleating protein from queens of the hornet,Vespula maculata

Abstract

Hemolymph ice nucleating factors are found in many freeze tolerant insects. These factors function to initiate ice nucleation in the extracellular fluid at fairly high subzero temperatures thereby minimizing the possibility of lethal intracellular ice formation. An ice nucleating protein was purified from the hymolymph of pupal bald faced hornets,Vespula maculata. This is the first ice nucleating protein to be purified. The protein has a molecular weight of 74,000, as determined by SDS-PAGE, and is quite hydrophilic. Glutamate and/or glutamine accounts for 20% of the amino acid residues. It is likely that the hydrophilic nature of the protein is involved in the ability of the protein to function as an ice nucleator.