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At least 1,243 records · Page 69Linked to original sources
PubMed1979

Role of prolactin the the expression of casein genes in the virgin rabbit.

Prolactin was injected into mature virgin rabbits. Casein mRNA, already present prior to the treatment was enhanced by prolactin. This accumulation of casein mRNA was not accompanied by a parallel significant synthesis of casein. Th effect of prolactin took place without a previous cellular multiplication. The mammary cell is therefore sensitive to prolactin before the first pregnancy but prolactin then displays only an abortive effect on the expression of casein genes.

Animals↗
PubMed1992

Identification of C-terminal peptides of bovine beta-casein that enhance proliferation of rat lymphocytes.

A casein polypeptidic fraction, obtained from a pepsin-chymosin digestion of caseins, showed a mitogenic effect on primed lymph node (LN) cells and unprimed spleen cells of rats. A biologically active C-terminal sequence of bovine beta-casein (residues 192-209) was characterized. The corresponding synthetic peptide had a stimulatory effect on primed LN cells but failed to enhance proliferation of spleen cells. We prepared two chymosin digests (PA and PB) of bovine beta-casein which contained, respectively, 80% and 95% of the sequence including residues 193-209. They induced a significant proliferative response in both LN and spleen cells. It is therefore possible that other active peptides in the PA preparation may be involved in mitogenic activity.

Amino Acid Sequence↗
PubMed1986

Characterization of a camel milk protein rich in proline identifies a new beta-casein fragment.

A camel milk whey protein has been isolated by reverse-phase high performance liquid chromatography. The protein is, like caseins, rich in proline (25% of the whole protein). The N-terminal amino acid sequence shows that the protein is homologous with a C-terminal region of beta-caseins analyzed from other species. The protein is concluded to be a fragment of beta-casein, derived from a non-tryptic type of cleavage of the parent molecule, and increasing the multiplicity of known casein products.

Amino Acid Sequence↗
PubMed1995

Expression of recombinant elongation factor 1 beta from rabbit in Escherichia coli. Phosphorylation by casein kinase II.

The beta subunit of eukaryotic elongation factor 1 (EF-1) catalyzes the GDP/GTP exchange activity on EF-1 alpha. In these studies, two cDNAs for the beta subunit of EF-1 from rabbit are cloned and sequenced. The cDNAs consist of 808 and 798 bp and are identical except for the 5' leader sequences of 67 and 57 bp. Both cDNAs code for a protein of 225 amino acids. Using the pT7-7 expression vector, EF-1 beta was expressed in Escherichia coli and purified to apparent homogeneity by chromatography on DEAE-cellulose and FPLC on Superose 12 and Mono Q. EF-1 beta was highly phosphorylated by casein kinase II, with up to 1.3 mol of phosphate incorporated per mol protein. From microsequence analysis and manual Edman degradation, the majority of the phosphate was shown to be present in serine 106 in the peptide DLFGS106DDEEES112EEA. Serine 112 was also phosphorylated by casein kinase II, but to a lesser extent. Previously, little phosphorylation of the beta subunit by casein kinase II was observed in native EF-1 unless GDP was bound to the alpha subunit (Palen, E., Venema, R.C., Chang, Y-W.E. and Traugh, J.A. (1994) Biochemistry, 8515-8520). In contrast, purified recombinant EF-1 beta was highly and specifically phosphorylated by casein kinase II; GDP and polylysine had little effect on the rate of phosphorylation of the purified subunit.

Amino Acid Sequence↗
PubMed1982

31P-NMR studies of bovine beta-casein.

Highly resolved 31P nuclear magnetic resonance spectra of the phosphoprotein bovine beta-casein and one of its phosphopeptides (residues 1-25) have been obtained with samples treated to remove paramagnetic metal ions. Spin-lattice (T1) and spin-spin (T2) relaxation times indicate little or no restriction to the segmental motion in the phosphoserine cluster region for both beta-casein and its phosphopeptide. The spectrum of beta-casein consists of four peaks over the pH range 5.7--8.0. The low-field peak has been assigned to Ser(P)-35 by comparison of the beta-casein and the phosphopeptide spectra. Interpretation of the NMR titration curves of 31P chemical shifts against pH in terms of a simple proton dissociation model is unsatisfactory. A two-site model in which it is assumed that the ionization of a phosphoserine residue is affected by the ionization neighbouring residues gives excellent fits to the titration data. The phosphoserine cluster residues (residues 15--19) have been assigned according to this interactive model.

Animals↗
PubMed1986

Identification of the sites on rabbit skeletal muscle protein phosphatase inhibitor-2 phosphorylated by casein kinase-II.

Inhibitor-2 was phosphorylated by casein kinase-II in vitro at a rate similar to that of glycogen synthase, a physiological substrate of this protein kinase. The major phosphorylation sites were identified as serines-86, -120 and -121, the peptide containing serines-120 and -121 being labelled about 2.5-fold more rapidly than that containing serine-86. The 13 residues C-terminal to serine-121 (SGEEDSDLSPEERE) contain seven acidic amino acids, while the six residues following serine-86 (SDTETTE) contain three. These results are consistent with the known specificity requirements of casein kinase-II. The three serines are C-terminal to the threonine (residue 72) whose phosphorylation by glycogen synthase kinase-3 is potentiated by prior phosphorylation with casein kinase-II. This reinforces the view that a C-terminal phosphoserine residue is important for the specificity of glycogen synthase kinase-3. Identification of the residues phosphorylated by casein kinase-II will facilitate further studies on the in vivo phosphorylation state of inhibitor-2.

Amino Acid Sequence↗
PubMed1990

The topography of bovine beta-casein at an oil/water interface as determined from the kinetics of trypsin-catalysed hydrolysis.

The topography of bovine beta-casein at a soya oil/water interface was studied by following the kinetics of the trypsin-catalysed hydrolysis. Tryptic peptides were identified from their amino acid compositions and the kinetics were compared with those obtained from beta-casein in solution. Whereas soluble beta-casein was initially hydrolysed at a number of trypsin-sensitive bonds, the hydrolysis of the protein at the interface was a more ordered event. The crucial initiating step was the cleavage of the N-terminal peptides 1-25 and 1-28 from the molecule. Hydrolysis at other trypsin-sensitive sites could then occur. This suggests that with the exception of the large hydrophilic moiety in the N-terminal region, most of the beta-casein molecule is inaccessible to the proteinase, and lies fairly flat on the oil/water interface. After removal of the N-terminal peptide, the remaining macropeptide can reorientate and other hydrophilic regions become accessible to the proteinase.

Amino Acids↗
PubMed1984

Induction of a substrate for casein kinase II during lymphocyte mitogenesis.

Particulate fractions prepared from concanavalin A-activated murine T lymphocytes contain an endogenous protein kinase that phosphorylates an endogenous protein substrate of Mr 112 000. The phosphorylation of 112 kDa protein is greatly reduced or absent in unstimulated T cells. Phosphoamino acid analysis indicates that 112 kDa protein is labeled on a serine. Add-back experiments using purified protein kinases indicate that 112 kDa protein serves as a substrate for casein kinase II. Phosphorylation of 112 kDa protein by the endogenous kinase is inhibited by heparin, a known casein kinase II inhibitor. The site or sites modified by the endogenous kinase and exogenous casein kinase II appear identical by peptide-mapping experiments. A time-course of the appearance of phosphorylated 112 kDa protein following stimulation with concanavalin A, measured in the presence or absence of added casein kinase II, suggests that 112 kDa protein is induced in activated T cells. Subcellular localization studies suggest that 112 kDa protein is a nuclear protein. Silver-binding and purification studies suggest that 112 kDa protein is of the nucleolar organizing region.

Animals↗
PubMed1988

Structure and phosphorylation of eukaryotic initiation factor 2. Casein kinase 2 and protein kinase C phosphorylate distinct but adjacent sites in the beta-subunit.

Eukaryotic initiation factor 2 (eIF-2) from rabbit reticulocytes can be phosphorylated on its beta-subunit by two different protein kinases, protein kinase C and casein kinase 2. Phosphorylation by these kinases is additive, suggesting that they phosphorylate different sites (serine residues) in eIF-2 beta. Two-dimensional peptide mapping of the phosphopeptides generated from labelled eIF-2 beta by digestion with trypsin, cyanogen bromide or Staphylococcus aureus V8 proteinase showed that protein kinase C and casein kinase 2 phosphorylated distinct and different sites in this protein. This conclusion was supported by the results of analysis of the phosphopeptides on reverse-phase chromatography. Analysis of the phosphopeptides derived from eIF-2 beta labelled by both kinases together strongly suggested that the sites labelled by protein kinase C and casein kinase 2 are adjacent in the primary sequence. These data are discussed in the light of the present understanding of the sequence specificity of the kinases. Rat liver eIF-2 beta was also found to be a substrate for protein kinase C and casein kinase 2, which were again shown to label different serine residues.

Amino Acid Sequence↗
PubMed1990

Characterization of three casein kinases type I from Dictyostelium discoideum.

Three different casein kinases type I have been characterized and partially purified from vegetative cells of Dictyostelium discoideum. The enzymes have been classified as type I because they are excluded from DEAE cellulose columns and do not utilize GTP as phosphoryl donor. We have named these activities as casein kinases IA, IB and IC respectively, according to the elution profile on phosphocellulose chromatography. The three activities differ in: the sensitivity to heparin inhibition; the salt optimum for activity and the amino acids phosphorylated, using casein as substrate. Experiments carried out in conditions that favor autophosphorylation indicate that casein kinase IB could have a 53 kDa subunit, susceptible to autophosphorylation in vitro.

Amino Acids↗
PubMed1990

General and histopathological results of a two-year study of rats fed semi-purified diets containing casein and soya protein.

Two semi-purified diets, identical except for protein (soya or casein), and a Purina chow diet were fed to groups of Sprague-Dawley rats and compared over a 22-month period for effects on body weight, organ weight, feed consumption, feed efficiency, protein efficiency, organ-to-body-weight ratios, certain organ mineral levels, gross pathology and histopathology. Feed efficiency, protein efficiency, body weight, and most organ weights were higher in the groups fed soya and casein, while feed consumption and most organ-to-body-weight ratios were relatively lower. Significant increases in the final pathology findings in the groups fed soya and casein included nephrocalcinosis (in females), hepatocellular vacuolization, gastric trichobezoars (hairballs), ulcerative pododermatitis (hock ulcers) and splenomegaly. This study demonstrates that the long-term feeding of semi-purified diets is feasible. Moreover, the differences observed between the protein sources, that is, soya and casein, were minimal, which suggests that either protein source is acceptable for long-term feeding studies.

Animals↗
PubMed1989

Complete nucleotide sequence of ovine beta-casein cDNA: inter-species comparison.

The complete nucleotide sequence of ovine beta-casein mRNA has been determined by sequencing, according to Sanger-Messing, both a recombinant clone isolated from a mammary cDNA pUC 18 library and a single-stranded cDNA generated by reverse transcription from a synthetic 17-mer primer complementary to the 5' part of the mRNA coding frame. The 1088 nucleotide long beta-casein mRNA, excluding the poly(A) tail, contains a coding frame of 669 nucleotides including the stop codon, flanked by 60 and 359 nucleotides in the 5' and 3' untranslated regions, respectively. It arises from the splicing of 9 exons as deduced from gene sequence data. The deduced amino acid sequence differs at 3 positions from that previously determined by direct sequencing of mature beta-casein. Comparison of the ovine, bovine, rat, mouse, and rabbit beta-casein mRNA sequences shows a higher homology in the 3' and 5' untranslated regions. The most conserved regions in the open reading frame are essentially those encoding the signal peptide and the major phosphorylation site.

Amino Acid Sequence↗
PubMed1990

A multinuclear, high-resolution NMR study of bovine casein micelles and submicelles.

High-resolution, natural abundance 13C[1H] (100.5 MHz), 31P[1H] (161.8 MHz) and 1H (400.0 MHz) NMR spectroscopy was used to identify the calcium-binding sites of bovine casein and to ascertain the dynamic state of amino acid residues within the casein submicelles (in 125 mM KCl, pD = 7.4) and micelles (in 15 mM CaCl2/80 mM KCl, pD = 7.2). The presence of numerous, well-resolved peaks in the tentatively assigned 13C-NMR spectra of submicelles (90 A radius) and micelles (500 A radius) suggests considerable segmental motion of both side chain and backbone carbons. The partly resolved 31P-NMR spectra concur with this. Upon Ca2+ addition, the phosphoserine beta CH2 resonance (65.8 ppm vs DSS) shifts upfield by 0.2 ppm and is broadened almost beyond detection; a general upfield shift (up to 0.3 ppm) is also observed for the 31P-NMR peaks. The T1 values of the alpha CH envelope for submicelles and micelles are essentially identical corresponding to a correlation time of 8 ns for isotropic rotation of the caseins. Significant changes in the 31P T1 values accompany micelle formation. Data are consistent with a loose and mobile casein structure, with phosphoserines being the predominant calcium-binding sites.

Animals↗
PubMed1996

Exon skipping in the ovine alpha s1-casein gene.

The reported cDNA sequences for the bovine (Bos taurus) and ovine (Ovis aries) alpha s1-caseins display a high degree of identity with the exception that a 24 bp region, corresponding to bovine exon 16, is absent in the ovine sequence. Here we show that the ovine gene for alpha s1-casein contains a sequence block displaying 23/24 identity to bovine exon 16, indicating that the absence of this block from ovine mRNA is due not to genomic deletion but to exon skipping. Analysis of the products obtained by reverse transcription of ovine alpha s1-casein mRNA followed by amplification, demonstrated the presence of mRNA species containing the exon 16 sequence as well as the species in which it had been spliced out. It was estimated that the latter constitutes 20% of the total ovine alpha s1-casein mRNA. We propose that a substitution within the donor splice site is responsible for the partial skipping of exon 16, possibly through the formation of an inhibitory RNA secondary structure.

Animals↗
PubMed1981

Cloning of mouse beta-casein gene sequences.

Casein messenger RNAs (mRNAcsn) were purified from lactating mammary glands of BALB/c mice and used as a starting material for cloning of casein gene sequences. Double-stranded casein cDNA (ds-cDNAcsn) was prepared and blunt-end ligated to HindIII-specific DNA linker molecules. After digestion with HindIII, the dsDNAcsn was inserted into the HindIII site of plasmid pBR322, using T4 DNA ligase. Escherichia coli strain RH202 was transformed with the hybrid plasmids, and transformants were selected for resistance to ampicillin. Electrophoresis of HindIII-digested hybrid plasmid DNAs, followed by Southern transfer and hybridization to [32P]cDNAcsn, revealed that one of the hybrid-plasmid-containing colonies, designated pCas51, contained a 400-bp insert which hybridized to the [32P]cDNAcsn. Purification of the individual casein mRNAs (mRNAcsn alpha, beta, and gamma) and solution hybridization of nick-translated insert DNA to each of these revealed that pCas51 contained sequences complementary primarily to mRNAcsn beta.

Animals↗
PubMed1989

Isolation and structural analysis of the mouse beta-casein gene.

Three overlapping clones containing the entire beta-casein gene were isolated from a mouse genomic library constructed in bacteriophage lambda EMBL3. Within the three clones the 6.8-kb casein gene was flanked by about 6-kb (5') and about 10-kb (3') sequences. The complete nucleotide sequence of the gene and its immediate flanking regions was determined. The gene consisted of nine exons ranging from 21 bp to 525 bp separated by introns ranging from 81 bp to 1288 bp. The length of the first exon was 43 bp, as determined by primer extension. The comparison of this sequence with that of the rat beta-casein gene showed that the overall structure of the gene was highly conserved. However, the first intron of the mouse gene was 400 bp shorter than that of the rat gene. Further analysis of homology between this gene and four other casein genes from rat and bovine revealed the presence of four highly conserved sequences. A search for the consensus sequences of transcription-regulatory elements showed that several potential regulatory sequences were present in the gene and its 5' flanking region.

Animals↗
PubMed1993

The complete sequence of the gene encoding bovine alpha s2-casein.

From a bovine genomic library, five overlapping clones, spanning some 50 kb, have been isolated. These clones contain the complete alpha s2-casein-encoding gene (alpha s2ca) and its 5' and 3' flanking regions. The nucleotide (nt) sequence of the complete gene including 2510 bp of the 5' flanking region and 276 bp of the 3' region has been determined. The total length of alpha s2ca appears to be 18483 bp and, therefore, it is the longest of the four bovine casein-encoding genes. The alpha s2ca gene is comprised of 18 exons ranging in size from 21 to 266 nt. There are 16 Alu-like artiodactyla retroposons inserted at ten different locations within the gene. About 14% of the gene is composed of these repetitive sequences. Although the organization of alpha s2ca appears to be similar to that of the alpha s1-casein-encoding gene (alpha s1ca), sequence comparisons and the length of the exons indicate that it is more closely related to the beta-casein-encoding gene. Furthermore, it is shown that both genes could have evolved from a common ancestor by means of internal duplications.

Animals↗
PubMed1992

Regional localization of human beta-casein gene (CSN2) to 4pter-q21.

Milk proteins are crucial for the development of all newborn mammals. Caseins that constitute the bulk of the protein in mammalian milk have been shown to be members of a multigene family in at least two species. They are among the most rapidly diverging groups of proteins, and their numbers vary widely among species. beta- and kappa-Caseins are the only caseins present in human milk. Using polymerase chain reaction on genomic DNA from somatic cell hybrids, we have localized the human beta-casein gene (CSN2) to 4pter----q21.

Blotting, Southern↗