Abstract
A major glycoprotein, CB-7+8 component, was selectively precipitated by dialyzing the fraction extracted with 1M KCl from the delipidated milk fat globule membrane against deionized water. The CB-7+8 contained 4.16% hexoses, 2.05% hexosamines and 2.08 sialic acid.
The CB-7+8 component was observed to be able to associate with the constituent poly-peptides of the soluble glycoprotein, PAS-I_??_VII and CB-III, and to form a soluble complex.
The CB-7+8 component which gave an apparently asymmetrical monopeak on sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed remarkable heterogeneity on iso-electric focusing, and six major bands of pI ranging from 5.9 to 6.8 were observed. The results of digestion of CB-7+8 with neuraminidase suggested that this heterogeneity was due to the microheterogeneity of oligosaccharide chains having a variable number of sialic acid residues.
