Abstract:
Unlike in other mammalian species, the major whey protein in
mouse is not alpha-lactalbumin, but a cysteine rich, acidic
protein with a molecular weight of 14.0 kDa. We have deduced the
amino acid sequence of this mouse acidic of whey protein from the
nucleotide sequence of cloned cDNA. The positions of the half
cysteines suggest that mouse whey acidic protein (WAP) is a two
domain protein, very similar in structure to the plant lectin
wheat germ agglutinin and the hypothalamic carrier protein
neurophysin.
Abstract:
We have characterized and cloned the lactation-specific mRNAs of
mouse mammary glands. The group of eight milk-protein-specific
mRNAs were identified (a) by size and antigenic properties of
their translation products in vitro and (b) by characterization
of their respective cDNA clones. Two alpha-caseins (43 kDa and 39
kDa) are encoded by mRNAs of 1600 nucleotides and two
beta-caseins (26 kDa) are encoded by mRNAs of 1450 nucleotides in
length. Three smaller caseins, gamma-casein (23.7 kDa),
delta-casein (21 kDa) and epsilon-casein (14.5 kDa) are
synthesized by mRNAs of 880, 1150 and 860 nucleotides. Beside
these casein mRNAs a mammary specific 620 nucleotide mRNA codes
for a novel acidic whey protein (13.7 kDa). cDNA clones
corresponding to the mRNAs for the lactation-specific proteins
have been isolated from a mammary-specific cDNA library. Cloned
alpha-casein cDNA hybridizes to both alpha-casein specific mRNAs
and cloned beta-casein cDNAs hybridize with both beta-casein
specific mRNAs. By RNA blot analysis we show that the cloned
cDNAs for mouse alpha-casein, beta-casein, gamma-casein and
epsilon-casein and the acidic whey protein cross-hybridize with
mRNAs of the rat, demonstrating partial sequence homology between
the corresponding mRNAs of those species.