Detection of Casein Phosphopeptides in Goat Milk

作者：Olumee Shabon Zohra^*; Boehmer Jamie L

来源：Journal of Proteome Research, 2013, 12(6): 3034-3041.

DOI：10.1021/pr3010666

• casein
• phosphotylation
• phosphoproteome
• post-translational modification
• milk
• mastitis

The aims of this study were to profile casein phosphopeptides in goat milk, to accurately determine the site of phosphorylation, and to evaluate whether or not any of the casein phosphorylation patterns were specific to a given physiological condition. Goat milk, collected before and after experimental induction of endotoxin mastitis, was separated by SDSPAGE. Casein bands were digested with trypsin and the resulting peptides were analyzed by nLC MS/MS. Eight out of nine predicted tryptic phosphopeptides corresponding to 18 different phosphorylation sites were detected in alpha(s1)-, a(s2)-, and beta-casein. Characterization of the phosphorylation sites illustrated the capability of tandem MS to accurately localize phosphorylated residues among a number of other putative sites. Despite an apparent lower abundance, almost all of the phosphopeptides were also detected in milk samples obtained from the goats following experimental induction of endotoxin mastitis. However, a tetraphosphopeptide in alpha(s2)-casein was only observed in the milk samples obtained from healthy animals. The absence of this multiphosphopeptide in the mastitic goat milk samples could indicate changes in phosphorylation as a result of disease and potentially be used as a marker for milk quality. This study represents the first comprehensive analysis of casein phosphoproteome and reveals a much higher level of phosphorylation than previously demonstrated in goat milk.

• 出版日期2013-6