A proteomic approach to evaluate the butyrophilin gene family expression in human milk fat globule membrane

Milk fat globule membrane (MFGM) contains proteins derived from the apical membrane of secreting epithelial cells of the mammary gland. Between 2 and 4% of tota human milk protein content is associated with the fat globule fraction, as MFGM proteins. While MFGM proteins have very low classical nutritional value, they play important roles in various cell processes and defence mechanism for the newborn. To date, fewer than 30 human MFGM proteins have been identified and characterized, either by immunological methods or by Edman sequencing and mass spectrometry. This study aimed to update the structural proteome of human colostral MFGM proteins and to create an annotated 2-DE MFGM protein database available on line. More than one hundred 2DE spots derived from human colostral MFGM proteins were investigated by MALDI-TOF mass spectrometry and proteins were identified by three different software packages available on the web (Peptident, MS-Fit and Profound); uncertain identifications were solved by nanoESI-ion trap mass spectrometry using Sequest software.