Structural studies on the freezing-point-depressing protein of the winter flounder Pseudopleuronectes americanus

The freezing-point-depressing protein from the winter flounder, Pseudopleuronectes americanus has been shown from circular dichroism measurements to possess a large proportion (∼85%) of the α-helical conformation in aqueous solution (pH 8.0) at −1°C. The helical content decreases as the temperature is raised. Viscosity data at −1°C indicate an asymmetric shape for the protein molecule compatible with its high helical content. Thus, the secondary and tertiary structure of this freezing-point-depressing protein as well as its primary structure (reported elsewhere), are found to be different from its counterpart glycoproteins isolated from the Antarctic fish.