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PubMed1982

Sequence of rat alpha- and gamma-casein mRNAs: evolutionary comparison of the calcium-dependent rat casein multigene family.

The complete sequences of rat alpha- and gamma-casein mRNAs have been determined. The 1402-nucleotide alpha- and 864-nucleotide gamma-casein mRNAs both encode 15 amino acid signal peptides and mature proteins of 269 and 164 residues, respectively. Considerable homology between the 5' non-coding regions, and the regions encoding the signal peptides and the phosphorylation sites, in these mRNAs as compared to several other rodent casein mRNAs, was observed. Significant homology was also detected between rat alpha- and bovine alpha s1-casein. Comparison of the rodent and bovine sequences suggests that the caseins evolved at about the time of the appearance of the primitive mammals. This may have occurred by intragenic duplication of a nucleotide sequence encoding a primitive phosphorylation site, -(Ser)n-Glu-Glu-, and intergenic duplication resulting in the small casein multigene family. A unique feature of the rat alpha-casein sequence is an insertion in the coding region containing 10 repeated elements of 18 nucleotides each. This insertion appears to have occurred 7-12 million years ago, just prior to the divergence of rat and mouse.

Amino Acid Sequence↗
PubMed1984

Effect of casein versus casein hydrolysate on mucosal adaptation following massive bowel resection in infant rats.

Little is known concerning the effects of elemental diets on bowel adaptation following massive resection. Fourteen of 28 Sprague-Dawley rats (40-45 g) were subjected to a 60% jejunoileal resection. Seven of the resected animals and seven sham-operated controls were then placed on a diet containing all protein in the form of casein hydrolysate. The remaining seven resected animals and seven sham-operated controls were placed on a comparable diet in which all the protein was casein. Each control animal was paired with a resected animal. After 2 weeks, unidirectional glucose and leucine transport was determined from intestinal sacs made from the proximal 3 cm and distal 3 cm of the remaining bowel. The midportion was used for the determination of mucosal weight and protein and sucrase content. When expressed as a percent increase over control values per centimeter of bowel, only sucrase levels were significantly elevated in the distal bowel in casein hydrolysate-versus casein-fed animals. The mucosal protein level, mucosal weight, and glucose uptake did not differ from control values when expressed as a percent change. Leucine uptake was significantly decreased in casein hydrolysate-fed animals when compared to that in casein-fed animals in both the proximal and distal bowel, again when expressed as a percent change from the control values. The administration of protein in the form of casein hydrolysate following massive bowel resection does not adversely affect mucosal hyperplasia occurring after resection but may have an adverse effect on the enhancement of amino acid absorption.

Adaptation, Physiological↗
PubMed1976

Effects of prolactin and progesterone on expression of casein genes. Titration of casein mRNA by hybridization with complementary DNA.

Prolactin injected into pseudopregnant rabbits induced lactogenesis. Progesterone injected simultaneously considerably reduced this effect. The content of mRNA for casein in total cellular RNA and in total polysomal RNA was estimated during these two hormonal actions using a hybridization technique. The synthesis of DNA complementary to casein mRNA was carried out with mRNA obtained from polysomes immunoprecipitated with anti-casein antibody. The content of casein mRNA was determined by hybridization of this cDNA with the RNA fractions. This technique revealed that prolactin induced the synthesis of mRNA for casein whereas progresterone greatly limited this effect of prolactin. These variations of casein mRNA content are in good agreement with values previously determined by translation and with the ability of mammary gland to synthesize casein.

Animals↗
PubMed1993

Characterization of rabbit kappa-casein cDNA: control of kappa-casein gene expression in vivo and in vitro.

The rabbit kappa-casein cDNA was cloned and sequenced. One of the isolated clones included almost the entire 5' end, while another clone corresponded to the 3' end of the cDNA. No polyadenylation site was found and therefore this clone did not harbour the complete cDNA. The amino acid sequence of a full-length protein was deduced from the nucleotide sequence obtained for this partial cDNA. It revealed the presence of a chymosin cleavage site and five potential phosphorylation sites. Rabbit kappa-casein was compared with those already described in other species. The rabbit sequence is closer to the ovine than to the mouse sequence. This result supports the idea that Lagomorpha are not closer to Rodentia than to Artiodactyla. The cDNA described above was used to study kappa-casein gene expression in the rabbit mammary gland. This expression was induced primarily by prolactin in mammary gland organoids and was similar to alpha s1-casein gene expression in vivo. The kappa-casein gene present in the casein gene locus is thus subject to the same regulation as the alpha s1-casein gene, although it has evolved from a fibrinogen gene.

Amino Acid Sequence↗
PubMed1976

Molecular weights of three mouse milk caseins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and kappa-like characteristics of a fourth casein.

Caseins of mouse milk are phosphoproteins which precipitate at pH 4.6, stain blue with "Stains-all," and stain red with "Stains-all" following alkaline phosphatase digestion. Four caseins were separated electrophoretically in sodium dodecyl sulfate-polyacrylamide gels varying from 8.5 to 15% acrylamide. Molecular weights for three of these proteins were 43,200, 27,700, and 25,900. The molecular weights determined for bovine alphas1 and beta caseins by this method were similar to those previously obtained by other methods. A fourth mouse casein contained carbohydrate, phosphorus, and sialic acid. This protein was rennin-sensitive and behaved anomalously on sodium dodecyl sulfate polyacrylamide gels, as did bovine kappa-casein. Because of similarities with bovine kappa-casein, it was designated with "kappa-casein" of mouse milk.

Animals↗
PubMed1979

Effect of voluntary exercise on physiological function and feeding behavior of mice on a 20% casein diet or a 10% casein diet.

The effects of voluntary exercise on growth and food intake, body composition, organ weight, and fatty acid composition of adipose tissue of mice fed on a 20% casein diet or a 10% casein diet were examined. The weight gain was greater for the 20% casein nonexercise group (20% NE) than that for the 20% casein exercise group (20% E), 10% casein exercise group (10% E) and 10% casein nonexercise group (10% NE). There were no significant differences between the groups except the 20% NE. In 20% E and 10% E, body fats decreased markedly. On the other hand, a very high ratio of protein was present in the body composition of both groups. In the 20% and 10% casein diet groups, food intake was increased by voluntary exercise, but there was no significant difference between 10%E and 10% NE except occasional periods during these experiments. After 6 weeks of age, 10% E had a tendency to undertake more voluntary exercise than 20% E, though the difference was not statistically significant. Development of the heart and gastrocnemius muscles was accelerated by voluntary exercise and epididymal fat tissue was markedly decreased.

Adipose Tissue↗
PubMed1985

Interactions in human casein systems: self-association of fully phosphorylated human beta-casein.

Human beta-casein was separated according to the extent of phosphorylation and the fully phosphorylated moiety was characterized. Fully phosphorylated human beta-casein makes up to 13-15% of the beta-casein fraction. It has a partial specific volume, v, of 0.754 +/- 0.008 and an absorbancy, E1(1%)cm,280 nm of 6.4 +/- 0.2. Sedimentation and viscosity data yield a solvation of 2.9 g H2O/g protein and an axial ratio of about 5 for the monomer. This would be consistent with a prolate ellipsoid of 10 nm length and 2 nm width. There is one strong binding site for Ca2+ for each organic phosphate ester in the molecule. The protein will precipitate at room temperature upon the addition of either 10 mM Ca2+ or greater than 1 M NaCl. Increasing the temperature from 4 to 37 degrees C causes an apparent conformational change and an increase in protein aggregation which is further increased by the addition of NaCl at this temperature until a limiting size is reached at about 0.25 M NaCl. This limiting size polymer contains 95-105 monomers and is nearly spherical with a radius of about 15 nm and a solvation of 3 g H2O/g protein. If this polymer were the submicelle of human casein, it could account for the abnormally high solvation of human casein micelles but their small average size would be more difficult to reconcile without additional information concerning K-casein association. The addition of Ca2+ to the system introduces association patterns which are more complex and not easily assessed.

Amino Acids↗
PubMed1998

Selection of an intact casein or casein hydrolysate diet by rats submitted to protein deprivation and bowel resection.

The feeding preference of normal rats (n = 14), malnourished rats (n = 14), and enterectomized rats (n = 16) was determined in a situation of free choice of three complete solid diets which only differed in extent of protein polymerization: intact casein, casein hydrolysate, and an amino acid mixture with a composition similar to that of casein. The animals were housed in metabolic cages for 30 days and allowed to freely choose among the three diets presented simultaneously. All three groups showed an initial preference for the intact casein diet. The control group maintained this preference, whereas the malnourished and enterectomized groups reduced the ingestion of the intact casein diet and increased the ingestion of the amino acid diet. The nitrogen balance, which was always positive in all three groups, was constant in the control group (1.51 +/- 0.26 g) initially higher (1.77 +/- 0.19 g) in the malnourished group, with a subsequent fall (1.13 +/- 0.24 g), and lower in the enterectomized group (0.83 +/- 0.32 g). Although total intake was similar for the control and malnourished groups, the malnourished group presented a higher weight recovery (130.2%). In contrast, the food intake of the enterectomized group was much lower, with a small weight gain. After treatment that impairs the digestive tract, intact casein was the initially preferred nitrogen source, which later tended to be replaced with free amino acids. This change was accompanied by an improvement in nitrogen balance and body weight, especially after protein malnutrition. These data may suggest that, in clinical practice, the use of enteral diets containing fully hydrolyzed protein may be of benefit in terms of the recovery of malnourished patients and of patients with short bowel syndrome.

Animals↗
PubMed1977

Fractionation of whole casein on hydroxyapatite. Application to a study of buffalo kappa-casein.

When whole caseins from cow and Italian buffalo (Bubalus arnee) were fractionated by chromatography on a column of hydroxyapatite they behaved in a similar manner. kappa-Casein was eluted with 5 mM phosphate buffer, pH 6-8, containing 0-2 M-KCl, 4-5 M-urea and 2 mM-2-mercaptoethanol, but beta- and alphas-caseins were retained and could be eluted successively by a linear gradient from 5 mM to 250 mM-phosphate buffer. Buffalo kappa-casein preparations, obtained from bulk milk or from milks of individual animals by chromatography on hydroxyapatite, produced identical electrophoretic patterns at pH 8-6. By further fractionation of these kappa-caseins on DEAE-cellulose, in each case, at least 7 components were purified; they had different electrophoretic mobilities but were all sensitive towards chymosin. The major fraction migrated like component 1 of bovine kappa-casein B.

Animals↗
PubMed1995

Effects of abomasal infusions of sodium caseinate and of casein hydrolysates varying in the relative proportions of peptides and free amino acids on milk production in dairy cows.

Two experiments were conducted to test the hypothesis that responses of milk production to the abomasal infusion of casein or hydrolysates of casein can be influenced by the proportion of peptide-bound amino acids in the infusate. Eight lactating cows were used in two Latin square experiments with period lengths of 10 d. In Expt 1, the four cows were at a late stage of lactation and the four treatments were a basal diet of silage and a barley-soya supplement alone or with infusions into the abomasum of 180 g/d of sodium caseinate, an enzymic hydrolysate of casein or an acid hydrolysate of casein; all treatments supplied equivalent amounts of all the amino acids, this being achieved by addition of free amino acids as required. As infused, the three treatments contained 89 (caseinate), 40 (enzymic hydrolysate) and 15 (acid hydrolysate) % of their amino acids as peptides. The increase of milk production in response to infusion was small and there were no significant differences between the infusion treatments. In Expt 2, the cows received a basal diet of grass silage and a supplement containing feather meal as the main source of protein. Treatments were the basal diet alone and with three infusion treatments as in Expt 1, except that the amount infused was 230 g/d. The response to infusion was greater in this experiment, there were significant differences between infusions and the yield of milk protein with the infusion treatments was linearly related (P = 0.001) to the proportion of peptide-bound amino acids in the infusate. Moreover, there was a close inverse relation (P = 0.007) between the proportion of peptide-bound amino acids in the infusate and the concentration of total peptide-bound amino acids in blood plasma.

Abomasum↗
PubMed1995

Effects of abomasal infusions of sodium caseinate, a hydrolysate of casein or a corresponding mixture of free amino acids on milk yield and composition in dairy cows.

The effects of the form in which amino acids are presented to the abomasum on the milk production of dairy cows receiving a basal diet of grass silage and a barley-based supplement were examined in two experiments. Effects of abomasal infusions of sodium caseinate were compared with the effects of corresponding levels of either an enzymic hydrolysate of casein (Expt 1) or a corresponding mixture of free amino acids (FAA; Expt 2). In Expt 1, although the yield of protein in milk increased progressively with each level of infusion, the yields of protein were greater for the caseinate than for the hydrolysate. Again, in Expt 2, for milk protein yield, sodium caseinate was superior to FAA at the lower level of infusion. In both experiments, the hydrolysate and FAA treatments were associated with higher concentrations of fat in the milk. There were indications of differences in the pattern of secretion of glucagon between the caseinate and FAA treatments. It is concluded that the differences between treatments relate either to the kinetics of absorption of amino acid residues or to the action of bioactive peptides released during digestion of casein.

Abomasum↗
PubMed2001

Gelation of casein-whey mixtures: effects of heating whey proteins alone or in the presence of casein micelles.

The aim of the present work was to investigate the role of whey protein denaturation on the acid induced gelation of casein. This was studied by determining the effect of whey protein denaturation both in the presence and absence of casein micelles. The study showed that milk gelation kinetics and gel properties are greatly influenced by the heat treatment sequence. When the whey proteins are denatured separately and subsequently added to casein micelles, acid-induced gelation occurs more rapidly and leads to gels with a more particulated microstructure than gels made from co-heated systems. The gels resulting from heat-treatment of a mixture of pre-denatured whey protein with casein micelles are heterogeneous in nature due to particulates formed from casein micelles which are complexed with denatured whey proteins and also from separate whey protein aggregates. Whey proteins thus offer an opportunity not only to control casein gelation but also to control the level of syneresis, which can occur.

Animals↗
PubMed2006

Bovine beta-casein (1-28), a casein phosphopeptide, enhances proliferation and IL-6 expression of mouse CD19+ cells via Toll-like receptor 4.

This study was conducted to elucidate the target cells and receptors which participate in the mitogenic and interleukin (IL)-6-enhancing effect of bovine beta-casein (1-28), a casein phosphopeptide. When the spleen lymphocyte subset (CD4+, CD8+, and CD19+ cells) from C3H/HeN mice was cultured with the beta-casein (1-28), it exerted a dose-dependent mitogenic effect on CD19+ cells. The effect of beta-casein (1-28) was not apparent in the case of CD19+ cells from C3H/HeJ mouse. In addition, the effect was significantly inhibited by treating the C3H/HeN mouse-derived CD19+ cells with neutralizing antibody for toll-like receptor 4 (TLR4). Reverse transcription-polymerase chain reaction analysis showed that the beta-casein (1-28) exerted an IL-6-enhancing effect on the CD19+ cells. The effect was also abrogated in either C3H/HeJ mouse-derived CD19+ cell culture or the anti-TLR4 antibody-added culture. These results suggest that the beta-casein (1-28) stimulates both proliferation and IL-6 expression of CD19+ cells via TLR4.

Animals↗
PubMed1984

Nucleotide sequence determination of guinea-pig casein B mRNA reveals homology with bovine and rat alpha s1 caseins and conservation of the non-coding regions of the mRNA.

Nucleotide sequence analysis of cloned guinea-pig casein B cDNA sequences has identified two casein B variants related to the bovine and rat alpha s1 caseins. Amino acid homology was largely confined to the known bovine or predicted rat phosphorylation sites and within the 'signal' precursor sequence. Comparison of the deduced nucleotide sequence of the guinea-pig and rat alpha s1 casein mRNA species showed greater sequence conservation in the non-coding than in the coding regions, suggesting a functional and possibly regulatory role for the non-coding regions of casein mRNA. The results provide insight into the evolution of the casein genes, and raise questions as to the role of conserved nucleotide sequences within the non-coding regions of mRNA species.

Amino Acid Sequence↗
PubMed1983

Failure of dietary-casein-induced acidosis to explain the hypercholesterolemia of casein-fed rabbits.

The partial replacement of casein by a mixture of gelatin, fish protein and soy protein in cholesterol-free semipurified diets of rabbits reduced the hypercholesterolemic response. The partial replacement of casein by the protein mixture also increased the feed intake and alleviated or reversed the weight loss observed from the casein diet. The data indicate that casein alone is not an ideal protein source for rabbits probably because of the imbalance of the amino acid composition. When KCl in the semipurified diets was replaced by KHCO3, a higher feed intake and a better growth were obtained, irrespective of the protein source in the diet. In addition, the feeding of semipurified diets containing KCl resulted in acidosis, which could be prevented by its replacement with KHCO3. A semipurified diet containing casein and KCl produced a more severe acidosis and higher serum cholesterol levels than the diet containing the protein mixture. Nevertheless, the correction of the acidosis by the replacement of KCl in the diet by KHCO3 did not lead to an abrogation of the casein-induced hypercholesterolemia.

Acidosis↗
PubMed1977

Bovine alpha s0 casein; a phosphorylated homologue of alpha s1 casein.

After consideration of its electrophoretic behaviour, amino acid composition and phosphate content, bovine alpha s0 casein has been shown to differ from alpha s1 casein only in respect of its phosphate content. The presence in alpha s0 casein of one phosphate residue more than occurs in alpha s1 casein was confirmed by comparative degradative studies performed on both proteins. From these it was concluded that alpha s0 casein may be considered as being alpha s1 casein which has been modified by phosphorylation of the seryl residue located at position 41.

Amino Acid Sequence↗
PubMed2006

DNA-remethylation around a STAT5-binding enhancer in the alphaS1-casein promoter is associated with abrupt shutdown of alphaS1-casein synthesis during acute mastitis.

Prolactin stimulates the expression of milk genes during lactation through the activation of STAT5 transcription factors, which subsequently bind to their cognate target sequence on the promoters. Demethylation of 5methylCpG dinucleotides permits the tissue-specific accessibility of transcription factor-binding sites during development, but remethylation has not been shown to contribute to acute suppression of gene expression. We characterize functionally a novel STAT5-binding lactational enhancer in the far upstream promoter (approximately -10 kbp) of the bovine alphaS1-casein-encoding gene. This promoter area is hypo-methylated in the lactating udder only. Remethylation of this area accompanies an experimentally elicited acute shutdown of casein synthesis in fully lactating cows, whose udder quarters have experimentally been infected with a pathogenic E. coli strain. Within 24 h after infection, the relevant promoter area was remethylated from 10% of the DNA molecules in the uninfected control quarters to approximately 50% in the infected quarters, the typical values for fully lactating and not lactating udders respectively. Increased methylation resulted in tighter chromatin packing. Concomitantly, the alphaS1-casein mRNA concentration dropped to approximately 50% while the protein synthesis was shut down to approximately 2.5% in the infected quarters, alone. The methylation status of the promoter from a not lactationally regulated gene was unaltered, and the distal alphaS1-casein promoter was not remethylated in udder quarters with subclinical Staphylococcus aureus infections featuring sustained casein synthesis. Hence, infection-related remethylation of the alphaS1-casein promoter and chromatin remodelling serves as an acute, spatially restricted regulatory mechanism, which might insulate the promoter against the systemically unchanged high levels of circulating prolactin. This provides a rare example for an acute regulatory significance of CpG methylation.

Acute Disease↗
PubMed1992

Interaction properties of doubly phosphorylated beta-casein, a major component of the human milk caseins.

Doubly phosphorylated beta-casein constitutes nearly 30% of the total human beta-caseins and is thus one of the major components of that fraction. The properties and mode of association of doubly phosphorylated beta-casein are therefore important determinants of the structure and function of the human casein micelle. Doubly phosphorylated beta-casein has an absorbency of 6.2 and a partial specific volume of .74. The protein precipitated at room temperature when 10 mM Ca2+ was added but produced a clear solution in 1 M NaCl. Equilibrium dialysis produced an average of 2.06 major Ca(2+)-binding sites at 37 degrees C with a dissociation constant of 12.1 x 10(-4) M. The monomer at 20 degrees C was calculated to have a solvation of 2.1 g of H2O/g of protein and an axial ratio of 6.8, suggesting a prolate ellipsoid of about 11 by 2 nm. At high ionic strength, evidence exists for a spherical structure with a molecular weight of 2.25 x 10(6). This structure would represent a polymer of about 90 monomers with a radius of 14.8 nm and a solvation of 1.93 g of H2O/g of protein. This association behavior is similar to that of other phosphorylated human beta-caseins but differs from the nonphosphorylated form. It changes when both Ca2+ and inorganic orthophosphate are present.

Calcium↗