Genetic modification of bovine β-casein and its expression in the milk of transgenic mice

Byung Kwon Choi, Gregory T. Bleck, Matthew B. Wheeler, Rafael Jiménez-Flores

Research output: Contribution to journalArticlepeer-review


Genomic vectors containing mutant bovine β-casein with putative glycosylation sites were constructed to study the functional properties of glycosylated β-casein and its possible effects in milk. The mutation was performed by PCR-based site-directed mutagenesis. The tripeptide sequence, Asn-X-Ser, was generated between Asn68 and Asn73 in mature β-casein. The resulting β-casein mutants were designated pCJB68 and pCJB6873. pCJB68 carries a substitution of Ser70 for Leu70 (Asn68-Ser69-Ser70-Pro71), and pCJB6873 carries a substitution of Ser70-Ser71 for Leu70-Pro71 (Asn68-Ser69-Ser70-Ser71). The two mutated genomic constructs were placed under control of the bovine α-lactalbumin promoter, and lines of mice expressing the pCJB68 and pCJB6873 have been established. The milk from transgenic mice contained bovine β-casein at levels up to 2-3 mg/mL. N-Linked glycosylation of bovine β-casein in the pCJB6873 line was confirmed by peptide-N-glycosidase F treatment, but glycosylation of bovine β-casein did not occur in pCJB68 mice. In addition, mouse casein micelles containing glycosylated bovine β-casein showed the largest median diameter and rough outer surface, compared to normal mouse casein micelles and micelles from transgenic milk containing bovine β-casein.

Original languageEnglish (US)
Pages (from-to)953-960
Number of pages8
JournalJournal of Agricultural and Food Chemistry
Issue number3
StatePublished - Mar 1996


  • Bovine β-casein
  • Site-directed mutagenesis
  • Transgenic

ASJC Scopus subject areas

  • Agricultural and Biological Sciences (miscellaneous)
  • Food Science
  • Chemistry (miscellaneous)


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