Studies on LM Protein appearing in Submandibular Glands of Isoproterenol-treated Rats. IV. Size and Shape Determination

Some physicochemical and biochemical properties of the purified large mobile (LM) protein appearing in submandibular glands of isoproterenol-treated rats were studied. The molecular weight of this protein was found by sedimentation equilibrium and gel chromatography on Sepharose 6B to be 12700-13000. The partial specific volume was estimated to be 0.72 and the Stokes radius to be 28.8 A. The frictional ratio of the LM protein was found to be 1.69 by viscometry by assuming that the hydration of the protein is zero and adopting a prolate ellipsoidal model. The circular dichroism spectra of the LM protein showed that most of the peptide chain took random coil (64%) and β-structure (30%) conformations. These results suggest that the LM protein has a slightly elongated shape. The LM protein did not show measurable activities of deoxyribonuclease, ribonuclease, lysozyme, nerve growth factor or phospholipase.