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Abstract
κ-Casein is the protein fraction of milk that allows formation of micelles and determines micelle size and function, thus affecting many of the physical characteristics of milk. Several lines of transgenic mice were generated bearing the B allele of the bovine κ-CN gene under the control of the regulatory sequences of the caprine β-CN gene that specifically directed expression of bovine κ-CN to the lactating mammary tissue of these mice. High expression of bovine κ-CN protein was observed in the lines studied; the total level of protein in milk was not significantly affected. A high degree of conservation in the amino acids involved in the predicted three-dimensional structure exists between murine and bovine κ-CN. Milk from transgenic lines expressing high bovine κ-CN had a significantly smaller micelle size than did control milk. Therefore, bovine κ-CN appears to have effectively participated in assembly of murine casein micelles. There was no effect on the time of rennet coagulation, but the association was significant between the milk of transgenic lines and the production of a stronger curd in rennet-induced gels. We conclude that bovine κ-CN is an appropriate candidate for transgenic technology that would increase the ratio of κ-CN to the calcium-sensitive caseins, therefore affecting the physical properties of the colloidal casein suspension.
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Article info
Publication history
Accepted:
January 17,
1996
Received:
August 28,
1995
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© 1996 American Dairy Science Association. Published by Elsevier Inc.
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