Purification and characterization of major glycoproteins, PAS-6 and PAS-7, from bovine milk fat globule membrane.
Two major glycoproteins (PAS-6 and PAS-7) from bovine milk fat globule membrane were selectively extracted with urea and KCl, co-purified by repeated gel filtration on Sephacryl S-200 and then separated by affinity chromatography on concanavalin A-agarose column. The two purified glycoproteins showed a single band by SDS-PAGE, and their molecular masses were estimated to be 50 kDa for PAS-6 and 47 kDa for PAS-7. Both PAS-6 and PAS-7 were resolved several variants by analytical isoelectric focusing. These were shifted to a single band at pI 6.2 for PAS-6 and at pI 6.5 for PAS-7 by neuraminidase. PAS-6 contained 7.1% and PAS-7 5.5% of carbohydrate; the molar ratio of fucose:mannose:galactose:N-acetyl galactosamine:N-acetyl glucosamine:sialic acid was 1.0:3.0:2.0:6.1:5.0:1.3 for PAS-6 and 1.0:3.1:2.2:0:4.1:1.1 for PAS-7. Mild alkaline treatment and affinity to various lectins indicated that PAS-6 had O- and N-linked oligosaccharide chains, while PAS-7 had only the N-linked type. The major amino acid residues of PAS-6 were Glu, Ser and Gly, and those of PAS-7 were Asp, Glu, Gly and Leu. The N-terminal amino acids of both glycoproteins were blocked. PAS-6 and PAS-7 digested with trypsin had a different peptide map, two major peptides having the same retention time on HPLC and being common to PAS-6 and PAS-7 having the same amino acid sequences of H-Gln-Ser-Gly-Asn-Lys-Asn-Pro-Ser-Glu-Ile-Ser-OH and H-Ile-Phe-Pro-Gly-Asn-Met-Asp-Asn-Ser-His-Lys-OH.
Kim
D H
DH
Department of Applied Biochemistry, College of Agriculture, Utsunomiya University, Japan.
Kanno
C
C
Mizokami
Y
Y
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002241:Carbohydrates / Q000032:analysis; D002850:Chromatography, Gel; D007526:Isoelectric Point; D037102:Lectins; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000302:isolation & purification*; D008892:Milk / Q000032:analysis*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D018396:Mucin-1; D009439:Neuraminidase; D010449:Peptide Mapping; D014357:Trypsin
D000596:Amino Acids; D002241:Carbohydrates; D037102:Lectins; D008562:Membrane Glycoproteins; D018396:Mucin-1; D009439:Neuraminidase; D014357:Trypsin