title: Characterisation of host defence proteins in milk using a proteomic approach.
abstract: Besides providing nutrition to the newborn, milk also protects the neonate and the mammary gland against infection. As well as the six major proteins, bovine milk contains minor proteins, not all of which have been characterized. In this study, we have subjected bovine skim milk, whey, and milk fat globule membrane (MFGM) fractions to both direct liquid chromatography-tandem mass spectrometry (LC-MS/MS), and two-dimensional electrophoresis (2-DE) followed by matrix assisted laser desorption ionization-time-of-flight (MALDI-TOF) mass spectrometry (MS) of individual protein spots to better characterize the repertoire of minor milk proteins, particularly those involved with host defense. Milk from peak lactation as well as during the period of colostrum formation and during mastitis were analyzed to gain a more complete sampling of the milk proteome. In total, 2903 peptides were detected by LC-MS and 2770 protein spots by 2-DE. From these, 95 distinct gene products were identified, comprising 53 identified through direct LC-MS/MS and 57 through 2-DE-MS. The latter were derived from a total of 363 spots analyzed with 181 being successfully identified. At least 15 proteins were identified that are involved in host defense. These results demonstrate that the proteome of milk is more complex than has previously been reported and a significant fraction of minor milk proteins are involved in protection against infection.
authors.affiliation: Dairy Science and Technology Section, AgResearch, Ruakura Research Centre, East Street, Hamilton, New Zealand.
authors.forename: Grant
authors.initials: G
authors.lastname: Smolenski
authors.forename: Stephen
authors.initials: S
authors.lastname: Haines
authors.forename: Fiona Y-S
authors.initials: FY
authors.lastname: Kwan
authors.forename: Jude
authors.initials: J
authors.lastname: Bond
authors.forename: Vicki
authors.initials: V
authors.lastname: Farr
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Davis
authors.forename: Kerst
authors.initials: K
authors.lastname: Stelwagen
authors.forename: Thomas T
authors.initials: TT
authors.lastname: Wheeler
mesh_terms: D000818:Animals; D000890:Anti-Infective Agents / Q000737:chemistry*; D002417:Cattle; D002853:Chromatography, Liquid; D003126:Colostrum / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D006017:Glycolipids / Q000378:metabolism; D006023:Glycoproteins / Q000378:metabolism; D007107:Immune System; D066292:Lipid Droplets; D013058:Mass Spectrometry; D008894:Milk Proteins / Q000737:chemistry* / Q000378:metabolism; D052756:Nutritional Sciences; D040901:Proteomics / Q000379:methods*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D000067816:Whey Proteins
chemical_list: D000890:Anti-Infective Agents; D006017:Glycolipids; D006023:Glycoproteins; D008894:Milk Proteins; D000067816:Whey Proteins; C110367:milk fat globule