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Purification and properties of the major sialoglycoprotein of the milk fat globule membrane

1977; Elsevier BV; Volume: 179; Issue: 2 Linguagem: Inglês

10.1016/0003-9861(77)90158-8

1096-0384

Lynn Snow, Douglas G. Colton, Kermit L. Carraway,

Carbohydrate Chemistry and Synthesis

The major periodate-Schiff positive component (glycoprotein-2) of bovine milk fat globule membranes (MFGM) has been purified by extraction of washed cream with chloroform/methanol followed by chromatography on Sephadex G-200 in sodium dodecyl sulfate. The glycoprotein is > 95% pure by polyacrylamide electrophoresis in dodecyl sulfate and shows the same prominent component at gel percentages of from 5 to 12.5. The molecular weight obtained by extrapolation of the apparent molecular weights on these gels to higher gel percentages was 70,000. An apparent molecular weight of 105,000 was obtained by gel filtration in 1% dodecyl sulfate on Sepharose 4B. The glycoprotein contains 50% carbohydrate by weight, with sialic acid (30.5%), N-acetylglucosamine (22.3%), galactose (15.9%), N-acetylgalactosamine (14.0%), mannose (11.1%), and fucose (5.8%) being the major monosaccharides. Leucine, glutamic acid, and glycine are the major amino acids. Affinity chromatography of deoxycholate-solubilized MFGM indicates that glycoprotein-2 is not the major concanavalin A receptor of these membranes.