title: Proteomic characterization and comparison of mammalian milk fat globule proteomes by iTRAQ analysis.
abstract: Milk fat globule membrane (MFGM) proteins are known to be involved in many biological functions; however, their components and inter-species complexity have not yet been completely elucidated. We investigated the protein composition of the MFGM-enriched fraction from Holstein, Jersey, yak, buffalo, goat, camel, horse, and human. Extracted proteins from the MFGM-enriched fractions were identified and quantified by an iTRAQ proteomic approach. We identified 520 protein species categorized as biological processes, cellular components and molecular function according to their annotation. Cellular process, localization, transport, signal transduction, and response to stimulus were the most common biological processes; binding and catalytic activities were the most prevalent molecular functions. Pathway analysis revealed several pathways, including glycolysis/gluconeogenesis, peroxisome proliferator-activated receptor signaling, and fatty acid biosynthesis. Quantified MFGM-enriched proteins were subjected to discriminative proteomic profiling by principal component analysis and a hierarchical clustering method, and then organized into four major clusters: (1) Holstein, Jersey, and yak milk; (2) buffalo and goat milk; (3) Holstein, Jersey, buffalo, yak, and goat milk; and (4) camel, horse, and human milk. These novel quantitative data provide insight into the protein composition of the MFGM and their potential physiological functions, and highlight the significant differences in the MFGM fractions among mammalian species.
  
  
  CONCLUSIONS
  Milk fat globule membrane (MFGM) proteins have exhibited a relatively larger diversity than other milk fractions, and implicated health beneficial effects. Proteomic analysis of MFGM protein was mainly focused on human, bovine and goat in previous studies. Recently, there is an increasing demand for natural milk from minor dairy animals. Differences in protein components were not yet elucidated that required the integration of this information across multiple species. Thus, iTRAQ analysis of the proteins in MFGM fractions from Holstein, Jersey, yak, buffalo, goat, camel, horse, and human was performed in this study. A total of 520 proteins were identified and quantified in the MFGM fractions. The results were contributed to a comprehensive overview and discriminative profiling of the MFGM proteome across species.
authors.affiliation: Ministry of Agriculture-Milk Risk Assessment Laboratory, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China; Institute of Animal Science and Veterinary Medicine, Anhui Academy of Agricultural Sciences, Hefei 230031, China.
authors.forename: Yongxin
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Ministry of Agriculture-Milk Risk Assessment Laboratory, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China; State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
authors.forename: Nan
authors.initials: N
authors.lastname: Zheng
authors.affiliation: Ministry of Agriculture-Milk Risk Assessment Laboratory, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China; Institute of Animal Science and Veterinary Medicine, Anhui Academy of Agricultural Sciences, Hefei 230031, China.
authors.forename: Xiaowei
authors.initials: X
authors.lastname: Zhao
authors.affiliation: Ministry of Agriculture-Milk Risk Assessment Laboratory, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China; State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
authors.forename: Yangdong
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Ministry of Agriculture-Milk Risk Assessment Laboratory, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China; College of Food Science and Engineering, Qingdao Agricultural University, Qingdao 266109, China.
authors.forename: Rongwei
authors.initials: R
authors.lastname: Han
authors.affiliation: Ministry of Agriculture-Milk Risk Assessment Laboratory, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
authors.forename: Lu
authors.initials: L
authors.lastname: Ma
authors.affiliation: Ministry of Agriculture-Milk Risk Assessment Laboratory, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China; State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
authors.forename: Shengguo
authors.initials: S
authors.lastname: Zhao
authors.affiliation: Ministry of Agriculture-Milk Risk Assessment Laboratory, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China; State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
authors.forename: Songli
authors.initials: S
authors.lastname: Li
authors.affiliation: Ministry of Agriculture-Milk Risk Assessment Laboratory, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
authors.forename: Tongjun
authors.initials: T
authors.lastname: Guo
authors.affiliation: Ministry of Agriculture-Milk Risk Assessment Laboratory, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China; State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China. Electronic address: wangjiaqinmqc@126.com.
authors.forename: Jiaqi
authors.initials: J
authors.lastname: Wang
mesh_terms: D000818:Animals; D002417:Cattle; D005260:Female; D006017:Glycolipids / Q000378:metabolism*; D006023:Glycoproteins / Q000378:metabolism*; D006801:Humans; D066292:Lipid Droplets; D008894:Milk Proteins / Q000378:metabolism*; D008895:Milk, Human / Q000378:metabolism*; D020543:Proteome / Q000378:metabolism*; D040901:Proteomics; D013045:Species Specificity
chemical_list: D006017:Glycolipids; D006023:Glycoproteins; D008894:Milk Proteins; D020543:Proteome; C110367:milk fat globule
keywords: Clustering; Mammal species; Milk fat globule membrane proteome; Quantitative proteomics