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PubMed2001

Analysis of Light Scattering Data on the Calcium Ion Sensitivity of Caseinate Solution Thermodynamics: Relationship to Emulsion Flocculation.

We describe the quantitative interrelation between the thermodynamic parameters of caseinate submicelles in the presence of calcium ions (0-14 mM) in aqueous medium and the capacity of the protein to induce depletion flocculation in oil-in-water emulsions at pH 7.0 and ionic strength 0.05 mol dm(-3). Measurements have been made by static and dynamic multiangle laser light scattering of the weight-average molecular weight, the radius of gyration, the hydrodynamic radius, and the second virial coefficient of caseinate submicelles in aqueous solution. Successive thermodynamic approximations with and without consideration of correlations between caseinate submicelles have been used to calculate the osmotic pressure in caseinate aqueous solutions and the free energy of the depletion interaction between droplets in oil-in-water emulsions stabilized by caseinate. Numerical results from both thermodynamic approximations are in reasonably good agreement with experiment, predicting a pronounced decrease in the strength of the depletion attraction at concentrations of Ca(2+) in the range 4-8 mM (with a minimum value at 8 mM). This correlates well with the great enhancement of stability of these emulsions with respect to flocculation in comparison with systems having no added ionic calcium and emulsions with lower (2 mM) or higher (10 mM) Ca(2+) contents. Nevertheless, the allowance for interactive correlations between caseinate submicelles seems to lead to a better prediction of emulsion flocculation on a qualitative level over the whole range of Ca(2+) concentrations studied (2-14 mM). The calculated pronounced decrease in depletion interaction strength is attributable to marked changes in weight-average molecular weight and mean size of aggregates, and to more positive values of the second virial coefficient of caseinate submicelles with increasing Ca(2+) content. Finally, we discuss the part played by the electrical charge on the protein in determining the overall strength of the flocculation-inducing attractive interactions between droplets. Copyright 2001 Academic Press.

Journal Article↗
PubMed2001

The Effect of pH on Monoglyceride-Caseinate Mixed Monolayers at the Air-Water Interface.

The surface pressure (pi) area (A) isotherms and Brewster angle microscopy (BAM) of monoglyceride-caseinate mixed films spread on buffered water at pH 5 and 7 and at 20 degrees C were determined as a function of the mass fraction (X) of monoglyceride (monopalmitin or monoolein) in the mixture. The structural characteristics, miscibility, and morphology of monoglyceride-caseinate mixed films are very dependent on surface pressure and monolayer composition. The monolayer structure was more expanded as the pH and the monoglyceride concentration in the mixture were increased. From the concentration and surface pressure dependence on excess area, free energy, and collapse pressure, it was deduced that, at a macroscopic level, monoglyceride (either monopalmitin or monoolein) and caseinate form a practically immiscible monolayer at the air-water interface. The BAM images and the evolution with the surface pressure of the relative reflectivity of BAM images give complementary information on the interactions and structural characteristics of monoglyceride-caseinate mixed monolayers, which at a microscopic level corroborated in part the conclusions derived from the pi-A isotherm at a macroscopic level. Over the overall range of existence of the mixed film the monolayer presents some heterogeneity due to the fact that domains of monoglyceride (especially of monopalmitin) and spots of collapsed caseinate residues are present during the monolayer compression-expansion cycle, giving relative intensity peaks with high relative film thickness. At higher pi, after the caseinate collapse, characteristic squeezing-out phenomenon was observed. At the monoglyceride monolayer collapse the mixed film is practically dominated by the presence of monoglyceride. The prevalence of monoglyceride in the interface increases with the amount of monoglyceride in the mixture and at higher pi. However, some degree of interactions exists between monoglyceride and caseinate in the mixed film and these interactions are more pronounced as the monolayer is compressed at the highest surface pressures. Copyright 2001 Academic Press.

Journal Article↗
PubMed1981

Effect of manganese and copper interaction on behavior and biogenic amines in rats fed a 10% casein diet.

Manganese chloride (1 mg manganese/ml drinking water) and copper sulphate (250 mg copper/kg diet) were administered daily for 30 days to growing rats maintained on a 10% casein diet. Manganese in combination with copper produced impairment in the learning ability and memory of rats in either dietary group, with greater alterations in those receiving a 10% casein diet. Hyperactivation due to the combined effects of the metal ions was identical in both dietary groups. The behavioral aberrations were associated with a marked accumulation of Cu in the brain of rats receiving the 10% casein diet. Combined exposure of Mn and Cu also produced a greater elevation in the levels of dopamine (DA) and norepinephrine (NE) and a depression of 5-hydroxytryptamine (5-HT) in the brain of animals fed with a 10% casein diet compared to the animals receiving the 21% casein diet. Thus the animals receiving the 10% casein diet appear to be more vulnerable to the neurotoxic effects of a combined exposure to manganese and copper. However rats maintained on the 21% casein diet and receiving both manganese and copper showed almost identical changes to those observed after manganese administration alone.

Animals↗
PubMed1998

Copresence of Deleted Protein Species Generates Structural Heterogeneity of Ovine alpha(s1)-Casein.

Multiple forms of mature alpha(s1)-casein have been characterized in ovine variants A and D using a combination of mass spectrometry and automated Edman degradation. Mature ovine alpha(s1)-casein was found to be a heterogeneous mixture of at least seven molecular species. The main component, representing about 50% total alpha(s1)-casein, corresponded to the full-length (199 residues long) protein. The other components were alpha(s1)-casein of different lengths: 198 (less Gln78), 191 (less peptide 110-117), 191 residues (less peptide 140-148), 190 (less peptide 110-117 and Gln78), 190 (less peptide 140-148 and Gln78), and 183 (less peptides 110-117 and 140-148) residues long alpha(s1)-casein. Each of the alpha(s1)-casein multiple forms occurred at three different phosphorylation levels, due to the partial phosphorylation of both Ser115 (at about 50%) and Ser41 (at about 20%). In the case of deleted peptide 110-117, the protein heterogeneity linked to the partially phosphorylated Ser115 was abolished, and only two levels of phosphorylation were observed. These multiple forms differing in molecular weight and degree of phosphorylation may have been developed from an exon skipping during mRNA splicing in ovine alpha(s1)-casein, similar to that recently described in the case of its caprine counterpart.

Journal Article↗
PubMed1993

Casein Kinase II-Type Protein Kinase from Pea Cytoplasm and Its Inactivation by Alkaline Phosphatase in Vitro.

A casein kinase II-type protein kinase has been purified from the cytosolic fraction of etiolated pea (Pisum sativum L.) plumules to about 90% purity as judged from Coomassie blue stained sodium dodecyl sulfate-polyacrylamide gels. This kinase has a tetrameric [alpha][alpha]'[beta]2 structure with a native molecular mass of 150 kD, and subunit molecular masses of 41 and 40 kD for the two catalytic subunits ([alpha] and [alpha]') and 35 kD for the putative regulatory subunit ([beta]).Casein and phosvitin can be used as artificial substrates for this kinase. Both serine and threonine residues were phosphorylated when mixed casein, [beta]-casein, or phosvitin were used as the substrate, whereas only serine was phosphorylated if [alpha]-casein or histone III-S was the substrate. The kinase activity was stimulated 130% by 0.5 mM spermine (the concentration required for 50% of maximal enzyme activity [A50] = 0.1 mM) and 80% by 2.5 mM spermidine (A50 = 0.4 mM), whereas putrescine and cadaverine had no effect. The kinase was very sensitive to inhibition by heparin (concentration for 50% inhibition [I50] = 0.025 [mu]g/mL). In contrast to most other casein kinase II-type protein kinases, this preparation was inhibited by K+ and Na+, with I50 values of 75 and 65 mM, respectively. Pretreatment of the purified kinase preparation in vitro with alkaline phosphatase caused a 5-fold decrease in its activity. Additionally, this kinase also lost its activity when its [beta] subunit was autophosphorylated in the absence of substrate. These results suggest that the activity of this casein kinase II protein kinase may be regulated by the phosphorylation state of two different sites in its multimeric structure.

Journal Article↗
PubMed1986

Comparative Study of Action of Cell Wall Proteinases from Various Strains of Streptococcus cremoris on Bovine alpha(s1)-, beta-, and kappa-Casein.

Partially purified cell wall proteinases of eight strains of Streptococcus cremoris were compared in their action on bovine alpha(s1)-, beta-, and kappa-casein, as visualized by starch gel electrophoresis, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and thin-layer chromatography. Characteristic degradation profiles could be distinguished, from which the occurrence of two proteinases, represented by strain HP and strain AM(1), was concluded. The action of the HP-type proteinase P(1) (also detectable in strains Wg(2), C(13), and TR) was established by electrophoretic methods to be directed preferentially towards beta-casein. The AM(1)-type proteinase P(III) (also detectable in strain SK(11)) was also able to degrade beta-casein, but at the same time split alpha(s1)- and kappa-casein more extensively than did P(I). Strain FD(27) exhibited mainly P(I) activity but also detectable P(III) degradation characteristics. The cell wall proteinase preparation of strain E(8) showed low P(I) as well as low P(III) activity. All proteinase preparations produced from kappa-casein positively charged degradation products with electrophoretic mobilities similar to those of degradation products released by the action of the milk-clotting enzyme chymosin. The differences between P(I) and P(III) in mode of action, as detected by gel electrophoresis and thin-layer chromatography, were reflected by the courses of the initial degradation of methyl-C-labeled beta-casein and by the effect of alpha(s1)- plus kappa-casein on these degradations. The results are discussed in the light of previous comparative studies of cell wall proteinases in strains of S. cremoris and with respect to the growth of this organism in milk.

Journal Article↗
PubMed2005

Experimental design applied for the simultaneous analysis of whey proteins and caseins of binary and ternary milk mixtures by capillary electrophoresis.

A capillary electrophoresis method for the simultaneous separation of caseins, whey proteins, and para-kappa-casein that appears during the manufacture of cheese was optimized using the response surface methodology. The parameters selected for this study were pH, voltage, and temperature. Under the optimized conditions (30 kV at 20 degrees C with 10 mM phosphate buffer at pH 3) casein proteins alpha(s)-casein; beta-casein, including genetic variants A1, A2, and B, kappa-CN, and para-kappa-CN; and whey proteins alpha-lactalbumin and beta-lactoglobulin (A and B variants) were separated. The method was applied successfully to skim milk, to casein precipitated at pH 4.6, and to a model sample containing rennet casein and milk. The milk used was of three types: cow, ewe, and goat. The present procedure can be easily applied to the separation of the major bovine, ovine, and caprine milk proteins in binary and ternary milk mixtures.

Algorithms↗
PubMed1997

Specific detection of an interleukin 1- and tumour necrosis factor-activated beta-casein kinase in HeLa and KB cells.

Interleukin 1 (IL-1) and tumour necrosis factor (TNF) activate a novel protein kinase, TIP kinase, which phosphorylates beta-casein in vitro. We have identified and purified to homogeneity a tryptic fragment of beta-casein, called T1, which was phosphorylated by TIP kinase with kinetics similar to those of the intact protein (K[m] = 27 +/- 6 microM). Phosphopeptide maps of in vitro phosphorylated T1 and beta-casein were identical, confirming that T1 contained the main phosphorylation site of the protein. T1 corresponded to residues 114 to 169 of beta-casein. It was phosphorylated by constitutively active protein kinases to a much lesser extent than beta-casein and thus constituted a specific substrate of the cytokine-activated enzyme. This made possible the detection of TIP kinase in extracts of IL-1-stimulated HeLa and KB cells, which had been hampered by high background phosphorylation when beta-casein was used as substrate. Our results show that the use of fragment T1 allows detection of low levels of TIP kinase in crude samples. They also suggest that its activation, which had previously been observed only in connective tissue cells, may be a general response of many cell types to IL-1 or TNF.

Casein Kinases↗
PubMed1995

Casein kinase I gamma subfamily. Molecular cloning, expression, and characterization of three mammalian isoforms and complementation of defects in the Saccharomyces cerevisiae YCK genes.

Casein kinase I, one of the first protein kinases identified biochemically, is known to exist in multiple isoforms in mammals. Using a partial cDNA fragment corresponding to an isoform termed CK1 gamma, three full-length rat testis cDNAs were cloned that defined three separate members of this subfamily. The isoforms, designated CK1 gamma 1, CK1 gamma 2, and CK1 gamma 3, have predicted molecular masses of 43,000, 45,500, and 49,700. CK1 gamma 3 may also exist in an alternatively spliced form. The proteins are more than 90% identical to each other within the protein kinase domain but only 51-59% identical to other casein kinase I isoforms within this region. Messages for CK1 gamma 1 (2 kilobases (kb)), CK1 gamma 2 (1.5 and 2.4 kb), and CK1 gamma 3 (2.8 kb) were detected by Northern hybridization of testis RNA. Message for CK1 gamma 3 was also observed in brain, heart, kidney, lung, liver, and muscle whereas CK1 gamma 1 and CK1 gamma 2 messages were restricted to testis. All three CK1 gamma isoforms were expressed as active enzymes in Escherichia coli and partially purified. The enzymes phosphorylated typical in vitro casein kinase I substrates such as casein, phosvitin, and a synthetic peptide, D4. Phosphorylation of the D4 peptide was activated by heparin whereas phosphorylation of the protein substrates was inhibited. The known casein kinase I inhibitor CK1-7 also inhibited the CK1 gamma s although less effectively than the CK1 alpha or CK1 delta isoforms. All three CK1 gamma s underwent autophosphorylation when incubated with ATP and Mg2+. The YCK1 and YCK2 genes in Saccharomyces cerevisiae encode casein kinase I homologs, defects in which lead to aberrant morphology and growth arrest. Expression of mammalian CK1 gamma 1 or CK1 gamma 3 restored growth and normal morphology to a yeast mutant carrying a disruption of YCK1 and a temperature-sensitive allele of YCK2, suggesting overlap of function between the yeast Yck proteins and these CK1 isoforms.

Amino Acid Sequence↗
PubMed2004

Gluten- and casein-free diets for autistic spectrum disorder.

BACKGROUND: It has been suggested that peptides from gluten and casein may have a role in the origins of autism and that the physiology and psychology of autism might be explained by excessive opioid activity linked to these peptides. Research has reported abnormal levels of peptides in the urine and cerebrospinal fluid of persons with autism. If this is the case, diets free of gluten and /or casein should reduce the symptoms associated with autism. OBJECTIVES: To determine the efficacy of gluten- and/or casein- free diets as an intervention to improve behaviour, cognitive and social functioning in individuals with autism. SEARCH STRATEGY: Electronic searching of abstracts from the Cochrane Library (Issue 3, 2003), PsycINFO (1971- May 2003), EMBASE (1974- May 2003), CINAHL (1982- May 2003), MEDLINE (1986- May 2003), ERIC (1965-2003), LILACS (to 2003) and the specialist register of the Cochrane Complementary Medicine Field (January 2004). Review bibliographies were also examined to identify potential trials. SELECTION CRITERIA: All randomised controlled trials involving programmes which eliminated gluten, casein or both gluten and casein from the diets of individuals diagnosed with autistic spectrum disorder. DATA COLLECTION AND ANALYSIS: Abstracts of studies identified in searches of electronic databases were read and assessed to determine whether they might meet the inclusion criteria. The authors independently selected the relevant studies from the reports identified in this way. As only one trial fitted the inclusion criteria, no meta-analysis is currently possible and data are presented in narrative form. MAIN RESULTS: The one trial included reported results on four outcomes. Unsurprisingly in such a small-scale study, the results for three of these outcomes (cognitive skills, linguistic ability and motor ability) had wide confidence intervals that spanned the line of nil effect. However, the fourth outcome, reduction in autistic traits, reported a significant beneficial treatment effect for the combined gluten- and casein- free diet. REVIEWERS' CONCLUSIONS: This is an important area of investigation and large scale, good quality randomised controlled trials are needed.

Autistic Disorder↗
PubMed2006

Formation of stable nanoparticles via electrostatic complexation between sodium caseinate and gum arabic.

The formation of electrostatic complexes between sodium caseinate and gum arabic (GA) was studied as a function of pH (2.0-7.0), using slow acidification in situ with glucono-delta-lactone (GDL) or titration with HCl. The colloidal behavior of the complexes under specific conditions was investigated using absorbance measurements (at 515 or 810 nm) and dynamic light scattering (DLS). In contrast to the sudden increase in absorbance and subsequent precipitation of sodium caseinate solutions at pH < 5.4, the absorbance values of mixtures of sodium caseinate and GA increased to a level that was dependent on GA concentration at pH 5.4 (pH(c)). The absorbance values remained constant with further decreases in pH until a sudden increase in absorbance was observed (at pH(phi)). The pH(phi) was also dependent upon the GA concentration. Dynamic light scattering (DLS) data showed that the sizes of the particles formed by the complexation of sodium caseinate and GA between pH(c) and pH(phi) were between 100 and 150 nm and these nanoparticles were visualized using negative staining transmission electron microscopy (TEM). Below pH(phi), the nanoparticles associated to form larger particles, causing phase separation. zeta-Potential measurements of the nanoparticles and chemical analysis after phase separation showed that phase separation was a consequence of charge neutralization. The formation of complexes between sodium caseinate and GA was inhibited at high ionic strength (>50 mM NaCl). It is postulated that the structure of the nanoparticles comprises an aggregated caseinate core, protected from further aggregation by steric repulsion of one, or more, electrostatically attached GA molecules.

Caseins↗
PubMed2003

Autoimmune uveitis induced by molecular mimicry of peptides from rotavirus, bovine casein and retinal S-antigen.

Antigenic mimicry of infectious agents and autoantigens is a proposed pathomechanism for autoimmune diseases. Here, we describe antigenic mimicry of a peptide from rotavirus, a nutritional protein from bovine milk (alphas2-casein) and a peptide thereof as well as a highly pathogenic peptide from retinal S-antigen (PDSAg), a major autoantigen in experimental autoimmune uveitis in Lewis rats. Immunization of rats with the peptides and the casein protein induced uveitis, an intraocular inflammation leading to decreased vision and even blindness. The peptides elicited cross-reactive T cell responses and uveitis in rats and were also recognized by lymphocytes and sera from uveitis patients. Oral tolerization with PDSAg, but not with rotavirus- and casein-derived peptides or casein protein, prevented PDSAg-induced uveitis in rats. Cofeeding of casein with cholera toxin induced uveitis in rats, suggesting that breaking oral tolerance to casein during gastrointestinal infections might also be able to initiate uveitis in humans.

Animals↗
PubMed1997

Inhibition of hepatocellular carcinoma development in hepatitis B virus transfected mice by low dietary casein.

In a comprehensive human ecological study, primary liver cancer has been shown to be highly significantly associated with 1) the prevalence of persistent infection with hepatitis B virus (HBV) and 2) plasma cholesterol concentrations that are, in turn, associated with the consumption of animal based foods. In rat studies, aflatoxin-induced hepatocellular carcinoma is substantially prevented by decreasing the intake of animal based protein (casein), a hypercholesterolemic nutrient. Thus the development of primary liver cancer associated with persistent HBV infection or with aflatoxin exposure may be controlled by reduced intake of animal-based proteins. Transgenic mice transfected with an HBV gene fragment containing the viral transactivator of hepatis B virus, HBx, which induces the formation of hepatocellular carcinoma, were used to examine the ability of dietary casein to modify tumor formation. Reducing the concentration of dietary casein to 6% from the traditional level of 22% markedly inhibited (by 75%) hepatic tumor formation in these transgenic mice. Tumor development also was substantially altered by interchanging dietary casein concentration well after tumor development had begun (at 8 months), increasing by 173% from the expected yield when casein intake was increased and decreasing by 99% when casein was reduced. These findings suggest that the development of liver tumor formation among individuals persistently infected with HBV may be controlled by minimizing or eliminating the intake of animal protein-based foods.

Animals↗
PubMed2005

Regulation by the extracellular matrix (ECM) of prolactin-induced alpha s1-casein gene expression in rabbit primary mammary cells: role of STAT5, C/EBP, and chromatin structure.

The aim of the present study was to understand how the extracellular matrix (ECM) regulates at the gene level the prolactin (Prl)-induced signal transducer and activator of transcription 5 (STAT5)-dependent expression of the alpha s1-casein gene in mammary epithelial cells. CCAAT enhancer binding proteins (C/EBPs) are assumed regulators of beta-casein gene expression. Rabbit primary mammary cells express alpha s1-casein gene when cultured on collagen and not on plastic. Similar C/EBPbeta, C/EBPdelta, STAT5, and Prl-activated STAT5 were found under all culture conditions. Thus the ECM does not act through C/EBPs or STAT5. This was confirmed by transfections of rabbit primary mammary cells by a construct sensitive to ovine prolactin (oPrl) and ECM (6i TK luc) encompassing STAT5 and C/EBP binding sites. The mutation of C/EBPs binding sites showed that these sites were not mandatory for Prl-induced expression of the construct. Interestingly, chromatin immunoprecipitation by the anti-acetylhistone H4 antibody (ChIP) showed that the ECM (and not Prl) maintained a high amount of histone H4 acetylation upstream of the alpha s1-casein gene especially at the level of a distal Prl- and ECM-sensitive enhancer. Alpha6 integrin (a membrane receptor of laminin, the principal active component of the mammary ECM) was found at the surface of cells cultured on collagen but not on plastic. In cells cultured on collagen in the presence of anti-alpha6 integrin antibody, Prl-induced transcription of the endogenous alpha s1-casein gene was significantly reduced, without modifying C/EBPs and STAT5. Besides, histone H4 acetylation was reduced. Thus, we propose that the ECM regulates rabbit alpha s1-casein protein expression by local modification of chromatin structure, independently of STAT5 and C/EBPs.

Animals↗
PubMed1989

Casein accumulation in distended rough endoplasmic reticulum of collagen gel-cultivated mouse mammary epithelia.

Mouse mammary epithelial cells cultivated on collagen gels synthesize and secrete casein in a hormone-dependent manner. Fine-structure electron microscopy of secretory cultures revealed numerous cytoplasmic structures surrounded by membrane that is studded with ribosomes. The structures appear to be distended rough endoplasmic reticulum (RER). Electron microscope protein A-colloidal gold immunolocalization showed casein antiserum-specific deposition of gold particles over the RER cytoplasmic vesicles in cells provided insulin, prolactin, and hydrocortisone (IPF). Nonimmune antiserum showed no gold particle deposition over these cytoplasmic structures. Epithelia provided only insulin showed no such cytoplasmic vesicles nor any specific deposition of gold particles. Immunoblot analysis of cell lysate and culture medium showed casein only in IPF-treated cultures. It appears that the casein secretory pathway in collagen gel cultured mammary epithelia is blocked at the step that fuses RER vesicles to Golgi membrane. The data raise questions regarding the processing and maturation of casein and the mechanism of casein secretion in these cultures.

Animals↗
PubMed1990

Tissue-specific decline in cytosolic casein kinase II of the ventral prostate in aging rats.

An age-associated decline in the activity of cytosolic casein kinase II in the rat ventral prostate was observed. The decrease in specific and total activity of casein kinase II of prostatic cytosol obtained from 12-month old rats compared with that from 3-month old rats was 50% and 70%, respectively. This decrease was tissue specific since no such alteration in enzymic activity was found in liver, lung, or heart. The decline in activity was not due to an increase in the concentration of a casein kinase inhibitor or to altered androgenic status with aging. Rather, the reduction in the activity of the enzyme was commensurate with the decrease in the total concentration of the enzyme protein as determined by an ELISA using anti-casein kinase II antibodies. The activity of casein kinase II in the nuclear fraction of the rat prostate was not altered in aging animals. It may be concluded that the cytosolic form of casein kinase II in the prostate of older animals is regulated at the transcriptional level (but not via the androgen-receptor complex mechanism). An alternative explanation for this observation may relate to altered stability of the enzyme in the prostate of older animals.

Aging↗
PubMed2005

Detection and characterization by high-performance liquid chromatography and mass spectrometry of a goat beta-casein associated with a CSN2 null allele.

The identification and characterization of a truncated goat beta-casein, associated with a null beta-casein allele (CSN2(O')), is reported. The truncated beta-casein predicted at the DNA level (NCBI Acc. No. CAB39313) but never observed at the protein level, here named beta-casein O, was detected as a minor component in a goat milk sample from an autochthonous breed from southern Italy, 'Rossa Mediterranea', by reversed-phase high-performance liquid chromatography/electrospray ionization mass spectrometry (RP-HPLC/ESI-MS). The ESI mass spectrum of the intact beta-casein O determined an M(r) value of 18 780 Da (calculated 18 781.5). Characterization of the amino acid sequence, performed by coupling trypsin digestion with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), RP-HPLC/ESI-MS and tandem mass spectrometry (MS/MS), demonstrated that the amino acid sequence corresponds to the 1-166 sequence of mature beta-casein variant A (Acc. No. P33048), thus confirming that the protein is coded by the null allele CSN2(O'), characterized by a transition (C --> T) at the 373rd nucleotide of the 7th exon of the gene, which generates a premature stop codon in position 182.

Alleles↗
PubMed1994

Casein kinase 2 and protein substrates are released from rat liver cells nuclei by DNase or RNase digestion.

Casein kinase 2 was released from rat liver cells nuclei by digestion with DNase I plus RNase A. This treatment also released three major substrates of 50, 40-42, and 37 kDa. Casein kinase 2 and substrates were also extracted by DNase or RNase separately. However, in DNase extracts only the 37 kDa protein was phosphorylated by casein kinase 2, whereas in RNase extracts all three substrates were phosphorylated. When the DNase extracts were subsequently treated with RNase the 40-42 substrates were then phosphorylated, indicating that their interaction with RNA prevents their phosphorylation by casein kinase 2. The ratio of B: alpha subunits of casein kinase 2 present in the nuclease extracts was higher than that of the purified enzyme, which is assumed to be 1:1. A further analysis by sucrose gradient centrifugation revealed that under physiological salt conditions casein kinase 2 from nuclease extracts formed large aggregates (higher than 300 kDa) which were disrupted at 400 mM KCl. At the latter KCl concentration CK-2 activity was localized at a position corresponding to a M(r) of 230-250 kDa, which is still higher than the typical tetrameric form of the enzyme.

Animals↗