Chromatographic separation of the proteins of mouse milk

Stevenson, Elizabeth M.; Leaver, J. D.

doi:10.1016/0958-6946(94)90013-2

Cited by 13 publications

(9 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…From one species to another, a large variability (quantitative as well as qualitative) is observed [3]. In human milk, there are only three caseins [4,5], whereas in murine and rabbit milks there are five [6,7]. These extreme situations reflect a general phenomenon which can take more subtle appearances, in which relative proportions of caseins may vary significantly between species and even between individuals, within species.…”

Section: Introductionmentioning

confidence: 99%

Translational efficiency of casein transcripts in the mammary tissue of lactating ruminants

Bevilacqua¹,

Helbling²,

Miranda³

et al. 2006

Reprod. Nutr. Dev.

View full text Add to dashboard Cite

-Caseins are essentially concentrated in the colloidal fraction of ruminant milks as highly hydrated and mineralized spherical particles, termed casein micelles. They form a group of four peptide chains (α s1 , β, α s2 and κ), encoded by four structural genes (CSN1S1, CSN2, CSN1S2 and CSN3, respectively) of which the expression is regulated by lactogenic hormones. These phosphoproteins are synthesized, essentially during lactation, in the mammary epithelial cells and we show, for the first time, that their regulation is also controlled at the translational level. Apparently, the four casein messenger are not translated with the same efficiency. Specific amplification systems have been developed and optimized to quantify, by real time quantitative PCR (qPCR), transcripts encoding the four caseins starting from total RNA extracted from mammary tissues taken on goats (n = 4), ewes (n = 3) and cows (n = 3), in lactation. The relative proportions of each specific messenger (% of casein mRNA) were compared to the relative amounts of the corresponding caseins (% of whole casein) in milks sampled from the same animals, determined after fractionation by reverse phase HPLC and integration of the corresponding peak areas. From qPCR data, the four casein transcripts appeared to be present approximately at the same level of abundance (ca. 25%, except for defective genotypes at the CSN1S1 locus, in the goat) whereas the amounts of the corresponding proteins in milk were ranging between 9 and 38% of the whole casein fraction. A comparison of specific translational efficiencies (% of protein in milk/% of transcript in the mammary tissue), showed that α s1 -and β-casein transcripts are translated ca. 3-to 4-fold more efficiently than α s2 -and κ-casein transcripts. This seems to be the rule in the three ruminant species studied. More or less optimal contexts for initiation of translation (Kozak recognition sequence of the start codon) as well as 3' untranslated region (UTR) sequences and length might explain, at least in part, our results. These preliminary results which have now to be confirmed with a larger number of individuals to strengthen our findings and conclusions, provides, however, a rational explanation to the unbalanced casein distribution (approximate proportions 4:1:4:1 for α s1 :α s2 :β:κ, respectively) reported for ruminant milks. The possible effects of specific secondary structures in the 5' and 3' UTRs of casein messengers still have to be considered. milk / casein / mRNA / quantification / untranslated regions (UTRs) / RP-HPLC / real time quantitative PCR / goat / cow / ewe

show abstract

Section: Introductionmentioning

confidence: 99%

Translational efficiency of casein transcripts in the mammary tissue of lactating ruminants

Bevilacqua¹,

Helbling²,

Miranda³

et al. 2006

Reprod. Nutr. Dev.

View full text Add to dashboard Cite

show abstract

“…Although the concentrations of individual free amino acids in milk are not equally dependent upon the stage of lactation in the human (18) and sow (19), the imbalance of free amino acids in milk has similarly been observed in a number of species (20). As compared with the amino acid compositions of mouse caseins (21), it is evident that free amino acids of LAO-convertible species (12,13,22) are few in mouse milk (20). The presence of LAO in milk remains unknown, but our hypothesis is that the imbalance of the free amino acid composition of milk is due to the LAO-catalyzed reaction of particular amino acids in the mammary gland.…”

mentioning

confidence: 99%

Characterization and Expression of l-Amino Acid Oxidase of Mouse Milk

Sun¹,

Nonobe²,

Kobayashi³

et al. 2002

Journal of Biological Chemistry

View full text Add to dashboard Cite

L-Amino acid oxidase (LAO) was purified from mouse milk. LAO reacted with L-amino acids in an apparent order of Phe > Met, Tyr > Cys, Leu > His > > other 11 amino acids tested and produced H 2 O 2 in a dose-and time-dependent manner. LAO in milk had a molecular mass of about 113 kDa and was converted to a 60-kDa protein by SDS-PAGE. LAO consisted of two subunits. The N-and C-terminal amino acid sequence determination followed by cDNA cloning showed that the 60-kDa protein consisted of 497 amino acids. LAO mRNA spanned about 2.0 kb, and its expression was found only in the mammary epithelial cells. Glucocorticoid was essential for LAO gene expression. Thus, the LAO gene is expressed acutely upon the onset of milk synthesis. LAO mRNA increased 1 day before parturition, peaked during early to mid-lactation, and decreased at the end of lactation. This is the first demonstration showing that LAO is present in milk. Mastitis is caused by an intramammary bacterial infection. As mouse milk produced H 2 O 2 using endogenous free amino acids, we suggest that LAO, together with free amino acids, is responsible for killing bacteria in the mammary gland.

show abstract

“…Conversely, the differences observed may effectively reflect the 'normal' variation associated with the expression of transgenes in the mammary gland in animals of a heterogeneous genetic background. As expected in all milk-producing animals, variation in the relative levels of the endogenous caseins from individual' mice has been reported (Stevenson and Leaver, 1994), and this, together with the variability produced during milking, may also account for the high intra-line variation observed in this study.…”

Section: Discussionmentioning

confidence: 64%

Expression of a bovine κ-CN cDNA in the mammary gland of transgenic mice utilizing a genomic milk protein gene as an expression cassette

Gutiérrez

Meade

DiTullio

et al. 1996

Transgenic Research

View full text Add to dashboard Cite

Transgenic mice were produced by microinjection of a DNA construct composed of the bovine kappa-casein (kappa-CN) cDNA under the control of the goat beta-CN 5' promoter elements and 3' flanking regions into pronuclear-stage embryos. The gene construct targeted the expression of bovine kappa-CN RNA to the mammary gland and secretion of bovine kappa-CN in the milk. In the three lines studied (BC-7, BC-31 and BC-67) the transgene was stably integrated and propagated as a Mendelian locus. Expression of the bovine protein in lactating mice from the three transgenic lines was demonstrated by northern and western blots. In ten different tissues analysed by northern blotting, expression was confined to the mammary gland of lactating transgenic mice from line BC-7, with low-level expression also observed in the salivary gland of lines BC-31 and BC-67. Transgene expression in the mammary gland paralleled normal casein gene expression during lactation and was not observed in virgin females. The level of bovine kappa-CN mRNA expression on day 10 of lactation in hemizygous transgenic females in relation to endogenous mRNA of whey acid protein (WAP) gene expression was 14%, 69%, and 127% in lines BC-7, BC-31 and BC-67, respectively. No association between transgene copy number and expression was observed. The bovine kappa-CN concentration in milk on day 10 of lactation ranged from 0.94 to 3.85 mg of protein per ml of milk. The bovine kappa-CN expressed in mouse milk had the same molecular mass and immunoactivity with polyclonal antibodies as did kappa-CN from bovine milk. A high degree of variation in the production of bovine kappa-CN within each of the transgenic lines was observed.

show abstract

Chromatographic separation of the proteins of mouse milk

Cited by 13 publications

References 35 publications

Translational efficiency of casein transcripts in the mammary tissue of lactating ruminants

Translational efficiency of casein transcripts in the mammary tissue of lactating ruminants

Characterization and Expression of l-Amino Acid Oxidase of Mouse Milk

Expression of a bovine κ-CN cDNA in the mammary gland of transgenic mice utilizing a genomic milk protein gene as an expression cassette

Contact Info

Product

Resources

About