Phosvitin

Egg yolk phosvitin and components of it, separated by countercurrent distribution, were subjected to a physical study to obtain information concerning the homogeneity of this protein with respect to molecular size and shape. 1. Both components of phosvitin sediment at the same rate as the unfractionated protein (s020,w = 3.7 S, corrected for the effect of selective solvation). 2. The diffusion coefficients of the major and minor phosvitin components appear to be slightly different (D20,w = 5.5 x 10-7 and 5.0 x 10-7 cm2 per sec, respectively). 3. No significant differences were found between the apparent partial specific volumes of the components of phosvitin and the unfractionated protein (V = 0.52 ml per g). 4. Analysis of sedimentation velocity data by the method of Fujita yielded results consistent with the conclusion that the components of phosvitin are very similar, if not identical, with respect to molecular size and shape. 5. The molecular weights of the major and minor phosvitin components were calculated as 36,000 and 40,000, respectively.