Phosphorylation and glycosylation isoforms of bovine κ-casein variant E in homozygous Swedish Red cow milk by liquid chromatography-electrospray ionization mass spectrometry
(2022) In Journal of Dairy Science 105(3). p.1959-1965- Abstract
Variations in the phosphorylation and glycosylation patterns of the common κ-casein (CN) variants A and B have been explored, whereas studies on variant E heterogeneity are scarce. This study reports for the first time the detailed phosphorylation and glycosylation pattern of the κ-CN variant E in comparison with variants A and B. Individual cow milk samples representing κ-CN genotype EE (n = 12) were obtained from Swedish Red cows, and the natural posttranslational modifications of its κ-CN were identified and quantified by liquid chromatography-electrospray mass spectrometry. In total, 12 unique isoform masses of κ-CN variant E were identified. In comparison, AA and BB milk consisted of 14 and 17 unique isoform masses, respectively.... (More)
Variations in the phosphorylation and glycosylation patterns of the common κ-casein (CN) variants A and B have been explored, whereas studies on variant E heterogeneity are scarce. This study reports for the first time the detailed phosphorylation and glycosylation pattern of the κ-CN variant E in comparison with variants A and B. Individual cow milk samples representing κ-CN genotype EE (n = 12) were obtained from Swedish Red cows, and the natural posttranslational modifications of its κ-CN were identified and quantified by liquid chromatography-electrospray mass spectrometry. In total, 12 unique isoform masses of κ-CN variant E were identified. In comparison, AA and BB milk consisted of 14 and 17 unique isoform masses, respectively. The most abundant κ-CN E isoform detected in the EE milk was the monophosphorylated, unglycosylated [1P 0G, ∼70%; where P indicates phosphorylation from single to triple phosphorylation (1–3P), and G indicates glycosylation from single to triple glycosylation (1–3G)] form, followed by diphosphorylated, unglycosylated (2P 0G, ∼12%) form, resembling known patterns from variants A and B. However, a clear distinction was the presence of the rare triphosphorylated, nonglycosylated (3P 0G, ∼0.05%) κ-CN isoform in the EE milk. All isoforms detected in variant E were phosphorylated, giving a phosphorylation degree of 100%. This is comparable with the phosphorylation degree of variants A and B, being also almost 100%, though with very small amounts of nonphosphorylated, glycosylated isoforms detected. The glycosylation degree of variant E was found to be around 17%, a bit higher than observed for variant B (around 14%), and higher than variant A (around 7%). Among glycosylation, the glycan e was the most common type identified for all 3 variants, followed by c/d (straight and branched chain trisaccharides, respectively), and b. In contrast to κ-CN variants A and B, no glycan of type a was found in variant E. Taken together, this study shows that the posttranslational modification pattern of variant E resembles that of known variants to a large extent, but with subtle differences.
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- author
- Sheng, Bulei ; Thesbjerg, Martin N. ; Glantz, Maria LU ; Paulsson, Marie LU ; Nielsen, Søren D. ; Poulsen, Nina A. and Larsen, Lotte B.
- organization
- publishing date
- 2022
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- genetic variants, glycan type, isoforms, posttranslational modifications
- in
- Journal of Dairy Science
- volume
- 105
- issue
- 3
- pages
- 1959 - 1965
- publisher
- American Dairy Science Association
- external identifiers
-
- scopus:85122453839
- pmid:34998567
- ISSN
- 0022-0302
- DOI
- 10.3168/jds.2021-21172
- language
- English
- LU publication?
- yes
- id
- 67f1db68-9bba-4dbe-a501-927c435d86ac
- date added to LUP
- 2022-02-08 14:32:18
- date last changed
- 2024-07-11 13:07:45
@article{67f1db68-9bba-4dbe-a501-927c435d86ac,
abstract = {{<p>Variations in the phosphorylation and glycosylation patterns of the common κ-casein (CN) variants A and B have been explored, whereas studies on variant E heterogeneity are scarce. This study reports for the first time the detailed phosphorylation and glycosylation pattern of the κ-CN variant E in comparison with variants A and B. Individual cow milk samples representing κ-CN genotype EE (n = 12) were obtained from Swedish Red cows, and the natural posttranslational modifications of its κ-CN were identified and quantified by liquid chromatography-electrospray mass spectrometry. In total, 12 unique isoform masses of κ-CN variant E were identified. In comparison, AA and BB milk consisted of 14 and 17 unique isoform masses, respectively. The most abundant κ-CN E isoform detected in the EE milk was the monophosphorylated, unglycosylated [1P 0G, ∼70%; where P indicates phosphorylation from single to triple phosphorylation (1–3P), and G indicates glycosylation from single to triple glycosylation (1–3G)] form, followed by diphosphorylated, unglycosylated (2P 0G, ∼12%) form, resembling known patterns from variants A and B. However, a clear distinction was the presence of the rare triphosphorylated, nonglycosylated (3P 0G, ∼0.05%) κ-CN isoform in the EE milk. All isoforms detected in variant E were phosphorylated, giving a phosphorylation degree of 100%. This is comparable with the phosphorylation degree of variants A and B, being also almost 100%, though with very small amounts of nonphosphorylated, glycosylated isoforms detected. The glycosylation degree of variant E was found to be around 17%, a bit higher than observed for variant B (around 14%), and higher than variant A (around 7%). Among glycosylation, the glycan e was the most common type identified for all 3 variants, followed by c/d (straight and branched chain trisaccharides, respectively), and b. In contrast to κ-CN variants A and B, no glycan of type a was found in variant E. Taken together, this study shows that the posttranslational modification pattern of variant E resembles that of known variants to a large extent, but with subtle differences.</p>}},
author = {{Sheng, Bulei and Thesbjerg, Martin N. and Glantz, Maria and Paulsson, Marie and Nielsen, Søren D. and Poulsen, Nina A. and Larsen, Lotte B.}},
issn = {{0022-0302}},
keywords = {{genetic variants; glycan type; isoforms; posttranslational modifications}},
language = {{eng}},
number = {{3}},
pages = {{1959--1965}},
publisher = {{American Dairy Science Association}},
series = {{Journal of Dairy Science}},
title = {{Phosphorylation and glycosylation isoforms of bovine κ-casein variant E in homozygous Swedish Red cow milk by liquid chromatography-electrospray ionization mass spectrometry}},
url = {{http://dx.doi.org/10.3168/jds.2021-21172}},
doi = {{10.3168/jds.2021-21172}},
volume = {{105}},
year = {{2022}},
}