Major proteins of the goat milk fat globule membrane

Representative pattern of goat milk fat globule membrane (MFGM) proteins in SDS-PAGE. Twenty-five micrograms of MFGM proteins were separated either on A) 10% or B) 6% SDS-PAGE and stained with Bio-Safe (Bio-Rad Laboratories, Hercules, CA). The MFGM proteins are from bovine (lanes 1–2) and caprine (lanes 3–4) milks. For identification, proteins were gel-digested by 0.2μg of trypsin, and peptides mixtures were subjected to matrix-assisted laser desorption/ionization–time of flight mass spectrometry analysis. Proteins identified with mass spectrometry were fatty acid synthase [FAS; accession number Q076H7 (Capra hircus)]; xanthine oxidase [XO; accession number A1YZ34 (Capra hircus)]; butyrophilin [BTN1A1; accession number A3EY52 (Capra hircus)]; lactadherin [LDH; accession number Q95114 (Bos taurus)]; and adipophilin [ADRP; accession number A6ZE99 (Ovis aries)]. Positions of protein standards (kDa) are indicated to the left of the panel.

Periodic acid–Schiff (PAS) staining of goat milk fat globule membrane proteins. Fifty micrograms of milk fat globule membrane proteins from bovine (lanes 1–2) or caprine (lanes 3–4) milks were loaded on 6% SDS-PAGE and stained with periodic acid–Schiff reagent. Because of codominant expression of variable-sized alleles, 1 or 2 equally stained bands for mucin-1 are visualized from individual milk samples. Positions of protein standards (kDa) are indicated to the left of the panel. MUC=mucin; CD36=cluster of differentiation 36; BTN1A1=butyrophilin; LDH=lactadherin; ADRP=adipophilin.

Characterization of butyrophilin and adipophilin from goat milk by immunoblotting. Twenty-five micrograms of milk fat globule membrane proteins were separated on 10% SDS-PAGE and electrotransferred onto nitrocellulose for immunoblotting with antibodies against A) bovine butyrophilin or B) mouse adipophilin, followed by appropriate secondary antibodies. Milk fat globule membrane proteins are from bovine (lanes 1–2) and caprine (lanes 3–4) milks. Positions of protein standards (kDa) are indicated to the left of the panel.