title: The relationships among bovine αS-casein phosphorylation isoforms suggest different phosphorylation pathways.
abstract: Casein (CN) phosphorylation is an important posttranslational modification and is one of the key factors responsible for constructing and stabilizing casein micelles. Variation in phosphorylation degree of αS-CN is of great interest because it is suggested to affect milk technological properties. This study aimed to investigate the variation in phosphorylation degree of αS-CN among milk of individual cows and to explore relationships among different phosphorylation isoforms of αS-CN. For this purpose, we analyzed morning milk samples from 529 French Montbéliarde cows using liquid chromatography coupled with electrospray ionization mass spectrometry. We detected 3 new phosphorylation isoforms: αS2-CN-9P, αS2-CN-14P, and αS2-CN-15P in bovine milk, in addition to the known isoforms αS1-CN-8P, αS1-CN-9P, αS2-CN-10P, αS2-CN-11P, αS2-CN-12P, and αS2-CN-13P. The relative concentrations of each αS-CN phosphorylation isoform varied considerably among individual cows. Furthermore, the phenotypic correlations and hierarchical clustering suggest at least 2 regulatory systems for phosphorylation of αS-CN: one responsible for isoforms with lower levels of phosphorylation (αS1-CN-8P, αS2-CN-10P, and αS2-CN-11P), and another responsible for isoforms with higher levels of phosphorylation (αS1-CN-9P, αS2-CN-12P, αS2-CN-13P, and αS2-CN-14P). Identifying all phosphorylation sites of αS2-CN and investigating the genetic background of different αS2-CN phosphorylation isoforms may provide further insight into the phosphorylation mechanism of caseins.
authors: GABI, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France; Animal Breeding and Genomics Centre, Wageningen University, PO Box 338, 6700 AH Wageningen, the Netherlands.
authors: Z H
authors: ZH
authors: Fang
authors: Animal Breeding and Genomics Centre, Wageningen University, PO Box 338, 6700 AH Wageningen, the Netherlands.
authors: M H P W
authors: MHPW
authors: Visker
authors: GABI, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France.
authors: G
authors: G
authors: Miranda
authors: GABI, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France.
authors: A
authors: A
authors: Delacroix-Buchet
authors: Animal Breeding and Genomics Centre, Wageningen University, PO Box 338, 6700 AH Wageningen, the Netherlands.
authors: H
authors: H
authors: Bovenhuis
authors: GABI, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France. Electronic address: patrice.martin@jouy.inra.fr.
authors: P
authors: P
authors: Martin
mesh_terms: D000818:Animals; D002364:Caseins; D002417:Cattle; D005260:Female; D008892:Milk / Q000737:chemistry*; D010766:Phosphorylation; D020033:Protein Isoforms / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D002364:Caseins; D020033:Protein Isoforms
keywords: casein; liquid chromatography coupled with electrospray ionization mass spectrometry; milk protein composition; phosphorylation