Sandbox WWCAlpha-S1-Casein
From Proteopedia
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| + | == Overview == | ||
'''Casein''' consists of a group of proteins found in all mammal milks, including αs1-, αs2-, and β-casein (calcium-sensitive caseins), κ-casein (calcium insensitive).<ref>J. Dairy Sci., 67, 1599-1631, 1984, and from Table 1, J. Dairy Sci., 68, 2195-2205, 1985</ref> Although αs1-CN is the predominant casein in bovine milk, the ratios of caseins vary considerably by species, and in human milk β-casein is predominant.<ref>doi: 10.1093/molbev/msr020</ref><ref>McSweeney, P. (2009). Nutritional Aspects of Milk Proteins. In Advanced dairy chemistry (3rd ed., Vol. 1). New York: Springer-Verlag.</ref> | '''Casein''' consists of a group of proteins found in all mammal milks, including αs1-, αs2-, and β-casein (calcium-sensitive caseins), κ-casein (calcium insensitive).<ref>J. Dairy Sci., 67, 1599-1631, 1984, and from Table 1, J. Dairy Sci., 68, 2195-2205, 1985</ref> Although αs1-CN is the predominant casein in bovine milk, the ratios of caseins vary considerably by species, and in human milk β-casein is predominant.<ref>doi: 10.1093/molbev/msr020</ref><ref>McSweeney, P. (2009). Nutritional Aspects of Milk Proteins. In Advanced dairy chemistry (3rd ed., Vol. 1). New York: Springer-Verlag.</ref> | ||
| - | + | == History == | |
| - | + | All caseins are in the secretory calcium-binding phosphoprotein (SCPP) family and share odontogenic ameloblast–associated (ODAM) protein as a common ancestor.<ref>doi: 10.1093/molbev/msr020</ref> ODAM is a SCPP involved in the mineralization of teeth, and has a primary structure rich in proline and glutamine. The caseins share this P/Q richness, giving the proteins a flexible, open structure <ref>Kawasaki K, Buchanan AV, Weiss KM. 2007. Gene duplication and the evolution of vertebrate skeletal mineralization. Cells Tissues Organs. 186:7–24.</ref> | |
| - | == Function == | + | == Biological Function == |
| + | Calcium-sensitive (CS) caseins such as αs1-CN bind calcium phosphate (CaP), and are precipitated by high concentrations of CaP. In milk, huge complexes are formed from CaP, calcium-sensitive caseins, and calcium-insensitive (CI) caseins. Precipitation of the CS caseins in these complexes is prevented by CI caseins stabilizing the complex to form a micelle. In addition to providing nutritive protein to mammalian neonates, these micelles supply calcium and inorganic phosphate at levels much higher than would be expected if the molecules were simply dissolved in the milk.<ref>McSweeney, P. (2009). Nutritional Aspects of Milk Proteins. In Advanced dairy chemistry (3rd ed., Vol. 1). New York: Springer-Verlag.</ref> Unlike whey proteins, which include all non-casein proteins, casein micelles are relatively heat stable, although denaturation of the whey protein β-lactoglobulin at high temperatures can result in interactions with micellar κ-casein that alters the structure of the micelle surface.<ref>Fennema, O. (1996). Characteristics of Milk. In Food chemistry (3rd ed., p. 865). New York: Marcel Dekker.</ref> | ||
| - | + | Preceding the formation of casein micelles, CS casein readily binds to the nuclei CaP forms CaP nanoclusters. It has been suggested that the rheomorphic (non-rigid) structure of CS caseins is what allows such efficient CaP binding.<ref>doi:10.1016/j.bbapap.2010.01.017</ref> On average 800 CaP nanoclusters are present in a casein micelle<ref>Smyth E, Clegg RA, Holt C. A biological perspective on the structure and function of caseins and casein micelles. Int J Dairy Technol 2004;57:121-126.</ref>, but this can vary considerably by species as the size of the micelle changes. | |
| - | == | + | == Function in Food == |
== Structural highlights == | == Structural highlights == | ||
Revision as of 02:49, 24 April 2015
Contents |
Overview
Casein consists of a group of proteins found in all mammal milks, including αs1-, αs2-, and β-casein (calcium-sensitive caseins), κ-casein (calcium insensitive).[1] Although αs1-CN is the predominant casein in bovine milk, the ratios of caseins vary considerably by species, and in human milk β-casein is predominant.[2][3]
History
All caseins are in the secretory calcium-binding phosphoprotein (SCPP) family and share odontogenic ameloblast–associated (ODAM) protein as a common ancestor.[4] ODAM is a SCPP involved in the mineralization of teeth, and has a primary structure rich in proline and glutamine. The caseins share this P/Q richness, giving the proteins a flexible, open structure [5]
Biological Function
Calcium-sensitive (CS) caseins such as αs1-CN bind calcium phosphate (CaP), and are precipitated by high concentrations of CaP. In milk, huge complexes are formed from CaP, calcium-sensitive caseins, and calcium-insensitive (CI) caseins. Precipitation of the CS caseins in these complexes is prevented by CI caseins stabilizing the complex to form a micelle. In addition to providing nutritive protein to mammalian neonates, these micelles supply calcium and inorganic phosphate at levels much higher than would be expected if the molecules were simply dissolved in the milk.[6] Unlike whey proteins, which include all non-casein proteins, casein micelles are relatively heat stable, although denaturation of the whey protein β-lactoglobulin at high temperatures can result in interactions with micellar κ-casein that alters the structure of the micelle surface.[7]
Preceding the formation of casein micelles, CS casein readily binds to the nuclei CaP forms CaP nanoclusters. It has been suggested that the rheomorphic (non-rigid) structure of CS caseins is what allows such efficient CaP binding.[8] On average 800 CaP nanoclusters are present in a casein micelle[9], but this can vary considerably by species as the size of the micelle changes.
Function in Food
Structural highlights
References
- ↑ J. Dairy Sci., 67, 1599-1631, 1984, and from Table 1, J. Dairy Sci., 68, 2195-2205, 1985
- ↑ Kawasaki K, Lafont AG, Sire JY. The evolution of milk casein genes from tooth genes before the origin of mammals. Mol Biol Evol. 2011 Jul;28(7):2053-61. doi: 10.1093/molbev/msr020. Epub 2011 Jan , 18. PMID:21245413 doi:http://dx.doi.org/10.1093/molbev/msr020
- ↑ McSweeney, P. (2009). Nutritional Aspects of Milk Proteins. In Advanced dairy chemistry (3rd ed., Vol. 1). New York: Springer-Verlag.
- ↑ Kawasaki K, Lafont AG, Sire JY. The evolution of milk casein genes from tooth genes before the origin of mammals. Mol Biol Evol. 2011 Jul;28(7):2053-61. doi: 10.1093/molbev/msr020. Epub 2011 Jan , 18. PMID:21245413 doi:http://dx.doi.org/10.1093/molbev/msr020
- ↑ Kawasaki K, Buchanan AV, Weiss KM. 2007. Gene duplication and the evolution of vertebrate skeletal mineralization. Cells Tissues Organs. 186:7–24.
- ↑ McSweeney, P. (2009). Nutritional Aspects of Milk Proteins. In Advanced dairy chemistry (3rd ed., Vol. 1). New York: Springer-Verlag.
- ↑ Fennema, O. (1996). Characteristics of Milk. In Food chemistry (3rd ed., p. 865). New York: Marcel Dekker.
- ↑ Uversky VN, Dunker AK. Understanding protein non-folding. Biochim Biophys Acta. 2010 Jun;1804(6):1231-64. doi:, 10.1016/j.bbapap.2010.01.017. Epub 2010 Feb 1. PMID:20117254 doi:http://dx.doi.org/10.1016/j.bbapap.2010.01.017
- ↑ Smyth E, Clegg RA, Holt C. A biological perspective on the structure and function of caseins and casein micelles. Int J Dairy Technol 2004;57:121-126.
