
%0 Journal Article
%A Stasiuk, Susan J. 
%A Summers, Emma L. 
%A Demmer, Jerome 
%T Cloning of a marsupial <font face="symbol">k</font>-casein cDNA from the brushtail possum (<emph type="2">Trichosurus vulpecula</emph>)
%J Reproduction, Fertility and Development
%D 2001/02/06
%V 12
%N 4
%P 215-222
%K 
%R https://doi.org/10.1071/RD99036
%U https://www.publish.csiro.au/paper/RD99036 
%X The main role of &kappa;-casein in milk is to stabilize the formation of casein micelles. Although marsupial milk contains casein micelles, &kappa;-casein had not been identified in any species. In these experiments, the first marsupial &kappa;-casein has been prepared as enriched casein fractions and the cDNA cloned from the brushtail possum (Trichosurus vulpecula). Possum &kappa;-casein is a 158 amino acid peptide that shares low amino acid sequence identity (20&#8211;30%) with that of eutherian &kappa;-caseins. In the gut of suckling young, casein micelles clot when &kappa;-casein is cleaved by chymosin at a specific site. Eutherian &kappa;-casein sequences are classified according to the sequence of the chymosin cleavage site: Phe-Met, Phe-Ile or Phe-Leu. Possum &kappa;-casein appears to form a separate class, with a putative chymosin cleavage site of Phe-Ala, which is different from that found in eutherian mammals. Other features of &kappa;-caseins, such as the location of the N-terminal cysteine, solubility in the presence of calcium, and the O-glycosylation sites on threonine residues in the C-terminus of the molecule, are conserved in the possum sequence. The &kappa;-casein gene was expressed throughout lactation in the mammary gland, and although mRNA levels of &kappa;-, &#945;- and &#946;-casein varied between animals there appeared to be a correlation in the expression of these genes within an individual animal. This suggests that a common transcription regulatory region may be controlling expression of all three genes in the possum. 
