Phosphorylation is a widespread posttranslational protein modification and is important in various biological processes. However, milk fat globule membrane (MFGM) phosphoproteins have not been explored systematically in human milk. Here, we used quantitative phosphoproteomics to analyze phosphorylation sites in human MFGM proteins and their differences at different stages of lactation; 305 phosphorylation sites on 170 proteins and 269 phosphorylation sites on 170 proteins were identified in colostrum and mature MFGM, respectively. Among these, 71 phosphorylation sites on 48 proteins were differentially expressed between the different stages of lactation. Osteopontin in human MFGM was the most heavily phosphorylated protein, with a total of 39 identified phosphorylation sites. Our results shed light on phosphorylation sites, composition, and biological functions of MFGM phosphoproteins in human colostrum and mature milk, and provide novel insights into the crucial roles of protein phosphorylation during infant development.

中文翻译：

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初乳和成熟乳中乳脂球膜的磷酸化蛋白质组学定量研究：泌乳期蛋白质磷酸化变化的新见解

磷酸化是广泛的翻译后蛋白质修饰，并且在各种生物学过程中很重要。但是，尚未在人乳中系统地研究乳脂球膜（MFGM）磷蛋白。在这里，我们使用定量磷酸化蛋白质组学来分析人类MFGM蛋白中的磷酸化位点及其在泌乳不同阶段的差异。在初乳和成熟MFGM中分别鉴定出170个蛋白质上的305个磷酸化位点和170个蛋白质上的269个磷酸化位点。其中，在哺乳的不同阶段之间，在48种蛋白质上的71个磷酸化位点差异表达。人MFGM中的骨桥蛋白是磷酸化程度最高的蛋白质，共有39个已确定的磷酸化位点。我们的结果揭示了磷酸化位点，组成，