Physicochemical Properties of Bovine Kininogen-II

1. The physicochemical properties ot purified bovine kininogen-II were studied. The molecular weight was calculated to be 46,600 from sedimentation and diffusion coefficients, 48,600 from the Scheraga-Mandelkern relation using β=2.12×lO⁶ and 47,000 by the Archibald method. These values are in good agreement with the value reported previously of 49,500 from amino acid analysis. The sedimentation and diffusion coefficients extrapolated to zero concentration were found to be 3.66 S and 6.16×10⁻⁷ cm.² sec.⁻¹, respectively. The partial specific volume, $υ¯$ , was 0.668 ml.μg. The intrinsic viscosity, [η] was 0.063 dl./g. at 25°C. The isoelectric point was determined by free boundary elec-trophoresis and found to be at pH 3.3. The electrophoretic mobility at pH 8.20 was −8.21 × 10⁻⁵ cm.² sec.⁻¹ volt⁻¹. The factional ratio, f/f_min , was 1.48, and the absorbancy, $E1cm.1%$, was 6.7 at 280 mpt. 2.The gross conformations of kininogen-II and of its derivatives were investigated by measurements of optical rotatory dispersion, circular dichroism and difference spectra. Kininogen-II has a low a-helical content and possibly has the α-structure in some part of the molecule, but when kinin is released enzymatically, the content of α-helix or β-structure of the residual protein increases. When the disulfide linkages in kininogen-II were completely reduced and carboxymethylated, the resulting RGM-kininogen had a quite different conformation from those of native and dekininated proteins.