PURPOSE: To obtain a novel shell protein of hawkbill turtle useful as a material for developing tortoise shell materials and as an immunogen by extracting the protein from the shells of hawkbill turtle with a solution mixture containing a denaturant and a reducing agent and purifying this protein in the presence of a denaturant and a reducing agent.

CONSTITUTION: The shells of hawkbill turtle is crushed with an atomizer to a powder, added with 20mM phosphate buffer solution (pH6.8) containing a denaturant (e.g. urea) and a reducing agent (e.g. dithiothreitol) and they are slowly stirred a day and overnight at 4°C to extract the protein, then the extract is centrifuged to collect the supernatant. The supernatant is subjected to an ion-change chromatography in the presence of a denaturant and a reducing agent to separate into an unadsorbed fraction and an adsorbed fraction, the adsorbed fraction is eluted and subjected to a reverse- phase high performance liquid chromatography to obtain a protein of formula I having molecular weight of 50000 and the unadsorbed fraction is subjected to a high performance liquid chromatography using an anion exchange column to collect the objective protein of formula II with a molecular weight of 15,000.