The major fat-globule membrane proteins, bovine components 15/16 and guinea-pig GP 55, are homologous to MGF-E8, a murine glycoprotein containing epidermal growth factor-like and factor V/VIII-like sequences.
The glycoproteins, Components 15/16 and GP 55, were partially purified from bovine and guinea-pig fat-globule membrane (FGM), respectively. Peptides prepared from immunoblots of Component 16 and GP 55, were shown by sequencing, to be similar to mouse MFG-E8 and a human milk protein of M(r) 46,000. Both of these latter proteins are associated with the FGM and contain epidermal growth factor-like domains and/or factor V/VIII-like sequences. These data complement earlier biochemical studies on the biosynthesis, tissue distribution and topology of Components 15/16 and GP 55, and indicate that MFG-E8-like proteins are expressed on the apical surfaces of mammary epithelial cells and are secreted both in a soluble form and as major components of the FGM in diverse species. The possible function of these proteins in lactation and in mammary and neonatal development is discussed.
Mather
I H
IH
Department of Animal Sciences, University of Maryland, College Park 20742.
Banghart
L R
LR
Lane
W S
WS
D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D003001:Cloning, Molecular; D003101:Collodion; D004247:DNA / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D004815:Epidermal Growth Factor / Q000235:genetics; D005165:Factor V / Q000235:genetics; D005169:Factor VIII / Q000235:genetics; D006168:Guinea Pigs; D006801:Humans; D008562:Membrane Glycoproteins / Q000235:genetics*; D051379:Mice; D008969:Molecular Sequence Data; D018396:Mucin-1; D017386:Sequence Homology, Amino Acid; D012967:Sodium Dodecyl Sulfate
D008562:Membrane Glycoproteins; D018396:Mucin-1; D012967:Sodium Dodecyl Sulfate; D004815:Epidermal Growth Factor; D005165:Factor V; D005169:Factor VIII; D003101:Collodion; D004247:DNA