Molecular weight determination and the secondary structure of the hypocalcemic protein purified from bovine parotid gland.

Abstract

Molecular weight determinations were carried out on a hypocalcemic protein purified from bovine parotid gland by sedimentation equilibrium, gel chromatography on Sepharose 6B in 6 M guanidine hydrochloride (Gun HCl) and viscometry in 6 M Gun HCl 0.1 M mercaptoethanol, and the values obtained were 45,000, 47,000 and 45,700, respectively. These results agreed well with the result (48,000) from sodium dodecyl sulfate polyacrylamide gel electrophoresis. The optical rotatory dispersion and circular dichroism spectra of the purified hypocalcemic protein showed that the contents of .alpha.-helix, .beta.-structure and random coil were 54, 26 and 20%, respectively. This protein contained large amounts of .alpha.-helix and thereby had a rigid structure.