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A genetic and biochemical analysis of a polymorphism of bovine αs2-casein

Published online by Cambridge University Press:  01 June 2009

François Grosclaude
Affiliation:
Laboratoire de Génétique biochimique, Institut National de la Recherche Agronomique, CNRZ, 78350 Jouy-en-Josas, France
Philippe Joudrier
Affiliation:
Laboratoire de Génétique biochimique, Institut National de la Recherche Agronomique, CNRZ, 78350 Jouy-en-Josas, France
Marie-Françoise Mahé
Affiliation:
Laboratoire de Génétique biochimique, Institut National de la Recherche Agronomique, CNRZ, 78350 Jouy-en-Josas, France

Summary

Using gel electrophoresis a genetic polymorphism of αs2-casein (Cn) was discovered in individual milk samples from 2 bovine breeds of the eastern part of France (Vosgienne and Montbéliarde). The 3 observed phenotypes (Plate 1) are determined by 2 co-dominant alleles at an autosomal locus. The αs2-Cn A variant was the only one known up to now in European breeds (reference variant) and ±s2-Cn D is a new variant, whose bands overlap the β-casein A band at pH 8.6, and migrate faster than αs2-Cn A at pH 3.0.

The sequence of the polypeptide chain αs2-Cn D differs from that of αs2-Cn A by the deletion of a very acidic nonapeptide, which includes a cluster of 3 phosphoseryl residues. Due to the characteristics of the reference sequence, this deletion cannot be exactly located but it involves residues 50–58, or 51–59, or 52–60.

A genetic analysis shows that locus αs2-Cn is closely linked to the cluster αsl-Cn–β-Cn-K-Cn. The 4 casein species are thus synthesized by 4 closely linked loci.

Type
Section B. Milk Proteins: Comparative Aspects, and the Study of some of the Minor Caseins
Copyright
Copyright © Proprietors of Journal of Dairy Research 1979

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References

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