MICROHETEROGENEITY AND SOME PROPERTIES OF MAJOR GLYCOPROTEIN FRACTION ISOLATED FROM BOVINE MILK-FAT GLOBULE MEMBRANE AFTER DELIPIDATION

A major glycoprotein, CB-7 +8 component, was selectively precipitated by dialyzing thefraction extracted with 1 M KCI from the delipidated milk fat globule membrane againstdeionized 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 polypeptideof 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 sodiumdodecyl sulfate-polyacrylamide gel electrophoresis showed remarkable heterogeneity on isoelectricfocusing, and six major bands of pI ranging from 5.9 to 6.8 were observed. Theresults of digestion of CB-7 +8 with neuraminidase suggested that this heterogeneity was dueto the microheterogeneity of oligosaccharide chains having a variable number of sialic acidresidues. © 1978, by the Agricultural Chemical Society of Japan.