Phosphoproteomics Revealed Differentially Expressed Sites and Function of the Bovine Milk Fat Globule Membrane in Colostrum and Mature Milk.

One type of large and intricate post-translational modification of milk proteins that has significant biological implications is phosphorylation. The characterization of phosphoproteins found in the bovine milk fat globule membrane (MFGM) is still mostly unknown. Here, label-free phosphoproteomics was used to identify 94 phosphorylation sites from 54 MFGM phosphoproteins in bovine colostrum (BC) and 136 phosphorylation sites from 91 MFGM phosphoproteins in bovine mature milk (BM). αs1-Casein and ß-casein were the most phosphorylated proteins in bovine colostrum. In bovine mature milk, perilipin-2 was the protein with the greatest number of phosphorylation sites. The results show that bovine colostrum MFGM phosphoproteins were mainly involved in immune function, whereas bovine mature MFGM phosphoproteins were mainly involved in metabolic function. Plasminogen and osteopontin were the most strongly interacting proteins in colostrum, whereas perilipin-2 was the most strongly interacting protein in bovine mature milk. This work demonstrates the unique alterations in the phosphorylation manner of the bovine MFGM protein during lactation and further expands our knowledge of the site characteristics of bovine MFGM phosphoproteins. This result confirms the value of MFGM as a reference ingredient for infant formula during different stages.

Proteomic and phosphoproteomic reveal immune-related function of milk fat globule membrane in bovine milk of different lactation periods.

Information regarding protein expression and phosphorylation modifications in the bovine milk fat globule membrane is scarce, particularly throughout various lactation periods. This study employed a complete proteome and phosphoproteome between bovine colostrum and mature milk. A total of 11 proteins were seen in both protein expression and phosphorylation levels. There were 400 proteins identified in only protein expression, and 104 phosphoproteins identified in only phosphorylation levels. A total of 232 significant protein characteristics were identified within the proteome and significant phosphorylation sites within 86 phosphoproteins of the phosphoproteome. Biological activities and pathways primarily exhibited associations with the immune system. Simultaneously, a comprehensive analysis of proteins and phosphorylation sites using a multi-omics approach. Hence, the data we have obtained has the potential to expand our understanding of how the bovine milk fat globule membrane might be utilized as a beneficial component in dairy products.