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PubMed1990

A novel synthetic substrate for casein kinase 2.

The nonapeptide DTDSEEEIR, corresponding to amino acid residues 78-86 of calmodulin, was synthesized, and its kinetics of phosphorylation by casein kinase 2 was examined. In the presence of 4 microM polylysine, the phosphorylation rate by casein kinase 2 was 16 times greater than that of synthetic substrate peptide RRREEETEEE reported previously, and almost 1 mol of 32p was incorporated per mol of nonapeptide in 60 min at 37 degrees C. The peptide was not phosphorylated by any other protein kinase. The Thr residue was phosphorylated by casein kinase 2, but Ser was not. The Km value of casein kinase 2 for the nonapeptide was 60 microM, comparable to that of casein, and Vmax for the nonapeptide was 4 times greater than that for casein. Addition of polylysine did not affect the Km value but markedly increased Vmax.

Amino Acid Sequence↗
PubMed1989

Immunohistochemical study of beta- and kappa-casein in the human breast and breast carcinomas, using monoclonal antibodies.

The immunohistochemical analysis of human beta- and kappa-caseins in the human breast, benign breast disease, and breast carcinomas is reported. The monoclonal antibodies LICR-LON-32.2 and LICR-LON-14.1 which react with human beta- and kappa-casein, respectively (Earl, H. M., and McIlhinney, R. A. J. Mol. Immunol., 22: 981-991, 1985) were used for these studies. Human beta- and kappa-caseins were detected in lactating human breast tissue, lactational foci in the resting breast, and heterogeneously in the 16th-week pregnant breast, but not in normal breast tissue. In benign breast disease occasional epithelial cells were demonstrated to synthesize beta- and kappa-caseins, but this finding did not appear to correlate with the hormonal status or previous obstetric histories of the patients. However, similar studies in 45 breast carcinomas with a wide range of estrogen receptor content, demonstrated no detectable beta- or kappa-casein. These results demonstrate that the caseins, which are biochemical markers of mammary gland differentiated function, and have been previously put forward as markers of breast cancer, were not synthesized in the 45 human breast carcinomas studied here, even in tumors with high levels of estrogen receptor protein.

Antibodies, Monoclonal↗
PubMed1987

Phosphorylation of serine 833 in cytoplasmic domain of low density lipoprotein receptor by a high molecular weight enzyme resembling casein kinase II.

A soluble protein kinase that phosphorylates the last serine residue (Ser-833) in the cytoplasmic domain of the low density lipoprotein (LDL) receptor was purified about 1300-fold from the cytosol of bovine adrenal cortex. The LDL receptor kinase shared several properties with casein kinase II: use of either GTP or ATP; phosphorylation of a typical casein kinase II recognition sequence in the LDL receptor (a serine followed by a cluster of three negatively charged amino acids); and inhibition by heparin. The LDL receptor kinase differed from classic casein kinase II in the following respects: its apparent molecular weight on gel filtration was approximately 500,000 as opposed to the usual molecular weight of 130,000 for casein kinase II; its affinity for the LDL receptor (apparent Km approximately 5 nM) was much greater than its affinity for casein (approximately 10 microM); and its activity was inhibited by polylysine, an agent that stimulates casein kinase II. The physiologic role of this unusual kinase, if any, is unknown.

Adenosine Triphosphate↗
PubMed1986

Tissue distribution of casein kinases.

The activities of casein kinases 1 and 2 in cytosol fractions prepared from 12 different rat tissues were compared. Casein kinase activities were detected in all tissues examined. Total casein kinase activities of lung, spleen, testis, and thymus were much higher than those of skeletal muscle, cardiac muscle, and adrenal gland. When activities of casein kinases 1 and 2 partially purified from lung, spleen, testis, and thymus prepared from 5 rats were compared, both total and specific activities of these kinases in testis were higher than those in the other tissues. These results indicate that testis is the most suitable tissue in rats for large-scale purification of casein kinase 1 as well as casein kinase 2.

Animals↗
PubMed1987

Tissue distribution of casein kinases.

The activities of casein kinases 1 and 2 in cytosol fractions prepared from 12 different rat tissues were compared. Casein kinase activities were detected in all tissues examined. Total casein kinase activities of lung, spleen, testis, and thymus were much higher than those of skeletal muscle, cardiac muscle, and adrenal gland. When activities of casein kinases 1 and 2 partially purified from lung, spleen, testis, and thymus prepared from 5 rats were compared, both total and specific activities of these kinases in testis were higher than those in the other tissues. These results indicate that testis is the most suitable tissue in rats for large-scale purification of casein kinase 1 as well as casein kinase 2.

Animals↗
PubMed1979

Lactose and casein content of nonpuerperal breast secretion.

Twenty-seven patients with nonpuerperal breast secretion were evaluated for the presence of casein and lactose in the secretions. Only two of seven patients with brownish or greenish secretions were positive for both lactose and casein although an additional six patients were positive for casein alone. Two patients with clear breast secretions were positive for both casein and lactose. However, 16 of 17 patients with milky or white secretions were positive for both casein and lactose. Although casein and lactose are more likely to be present in white breast secretions, other types of breast secretions may also contain these constituents.

Adolescent↗
PubMed1978

Site-specific phosphorylation of beta-casein by proetin kinases from rabbit reticulocytes.

The B variant of beta-casein was phosphorylated with [gamma-32P]ATP using four different protein kinases isolated from rabbit reticulocytes. Casein was maximally phosphorylated by the individual protein kinase activities and subjected to chymotrptic digestion. The peptides were separated by a two-dimensional peptide fingerprinting technique, and the phosphorylated peptides were identified by autoradiography, The two phosphorylated peptides obtained from the action of casein kinase I were shown to have different migration patterns from those obtained with casein kinase II. The cAMP-regulated protein kinases had the same substrate specificity with beta-casein B, and the two phosphorylated peptides obtained using these enzymes were distinct from those phosphorylated by the cAMP-independent enzymes. Thus, the different protein kinases can be identified by substrate specificity using beta-casein.

Animals↗
PubMed1984

Phosphorylation of the C-proteins of HeLa cell hnRNP particles. Involvement of a casein kinase II-type enzyme.

The phosphorylation of the proteins of heterogeneous nuclear ribonucleoprotein particles has been investigated in HeLa cells. 32Pi labeling of intact cells indicated that, of the six major particle proteins, the most heavily phosphorylated was the C1-protein (Mr = 42,000). This protein, together with C2 (Mr = 44,000), is also phosphorylated by [gamma-32P]ATP in particle extracts and in particles that are purified by sedimentation or exclusion chromatography. The C-proteins, together with their particle-associated kinase, were partially purified from isolated particles following dissociation with micrococcal nuclease. Proteins C1 and C2 co-purify on phosphocellulose chromatography, and their peak overlaps with that of a casein kinase activity. Evidence suggesting that this kinase activity is responsible for C-protein phosphorylation includes 1) the phosphorylation of C-proteins in the fractions where they overlap with the kinase, 2) the phosphorylation of added C-protein by fractions of the casein kinase which lack detectable C-protein, and 3) the similarities in catalytic properties of the casein kinase- and C-protein-phosphorylating activities. The purified kinase activity is cyclic nucleotide and Ca2+ independent. It is stimulated by polyamines, inhibited by heparin, and utilizes either GTP or ATP with high affinity. Serine residues are the major phosphate acceptors. These properties indicate that the kinase is casein kinase II or a closely related enzyme. Moreover, purified casein kinase II from rabbit liver effectively phosphorylates C-protein. These results suggest that C-proteins may be natural substrates for nuclear casein kinase II.

Adenosine Triphosphate↗
PubMed1984

Physiological casein and gluten protein requirements of growing rats.

Using mounting casein and wheat gluten protein values (0-40%) in the animals' diet, the optimum and minimum physiological daily doses were determined in 49-day-old growing rats from changes in their body water, body nitrogen and protein intake. The optimum physiological doses were identical with the peak of linearity of the given parameters, which coincided with a 15% casein protein and a 20% gluten protein concentration in the diet. This was also confirmed by the maximum body amino acid values, which were found in animals given a 15% casein or 20% gluten protein diet. It was further confirmed by the finding of significantly elevated alanine aminotransferase and aspartate aminotransferase activity in the liver of animals with a higher intake of the above protein sources. The minimum physiological dose of the given protein was determined from the equations of the regression curves in the presence of zero changes in the body nitrogen or body water content. The optimum physiological daily doses of casein and wheat gluten protein were 3.25 g and 4.05 g respectively. The minimum physiological daily doses of casein protein were 268 mg (from body nitrogen changes) and 371 mg (from body water changes) and the minimum physiological daily doses of gluten protein were 892 mg (from body nitrogen changes) and 1,000 mg (from body water changes). The above indicators demonstrate, in the presence of higher and high dietary concentrations, that an intake of the given proteins over and above the optimum physiological daily dose is at the very least uneconomical (gluten), if not harmful (casein), making this a highly topical problem for further study.

Aging↗
PubMed1983

Oligomeric structure and catalytic activity of G type casein kinase. Isolation of the two subunits and renaturation experiments.

Casein kinase G purified from bovine tissue is an oligomeric cyclic nucleotide-independent protein kinase made of two different monomers, namely an alpha (Mr = 38 kilodaltons) and a self-phosphorylatable beta (Mr = 27 kilodaltons) subunit. Treatment of the native enzyme under denaturing conditions (0.5 M NaCl, 4 M LiCl, and 20 to 35% formamide) resulted in a progressive selective removal of the beta subunit following gel filtration and a correlated loss of activity of the corresponding renatured enzyme. Mild digestion with papain resulted in a proteolytic alteration limited to the beta monomer with a concomitant partial loss of the enzyme activity. Isolation of the alpha and beta casein kinase G subunits was achieved by preparative reversed polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Renaturation of the proteins following sodium dodecyl sulfate removal by acetone and/or Triton X-100 treatment allowed reconstitution of a functional casein kinase G. Whereas the isolated alpha subunit was found to exhibit a weak catalytic activity, addition of the beta subunit was required for recovery of a maximal casein kinase activity. The process was dose-dependent and reached a plateau for an alpha:beta subunit molar ratio of approximately 1 to 1. These data suggest that while the casein kinase G alpha subunit bears the catalytic site, stoichiometric combination with the beta subunit is required for optimal enzymatic activity. A possible role of the beta subunit as a regulatory component of casein kinase G activity in the intact cell remains to be examined.

Animals↗
PubMed1984

Regulation of casein kinase II by 2,3-bisphosphoglycerate in erythroid cells.

The hemoglobin regulator, 2,3-bisphosphoglycerate (glycerate-2,3-P2) has been shown to modulate the activity of casein kinase II from rabbit reticulocytes. Kinetic results were obtained with the exogenous substrate, beta-casein and the endogenous substrates, initiation factors (eIF-) 2 and 3. Experiments carried out to determine the interaction between glycerate-2,3-P2, Mg2+, substrate, and casein kinase II led to the following conclusions: 1) glycerate-2,3-P2 inhibition was competitive with respect to the protein substrate and noncompetitive with respect to ATP; 2) inhibition was not caused by depletion of ATP-Mg2+ as a consequence of Mg2+ complexation with glycerate-2,3-P2; 3) the response curve for glycerate-2,3-P2 was cooperative, but the cooperativity decreased as salt concentration increased; 4) glycerate-2,3-P2 inhibition was dependent on Mg2+ concentration up to about 5 mM MgCl2 but did not parallel glycerate-2,3-P2 X Mg2+ complex formation indicating that the Mg2+ dependence was not due to the formation of a glycerate-2,3-P2 X Mg2+ complex; 5) experiments with analogs of glycerate-2,3-P2 showed that the binary phosphate grouping was important in determining inhibition by glycerate-2,3-P2 while the presence of the carboxylate-phosphate pair was much less important; 6) low levels of glycerate-2,3-P2 stimulated phosphorylation of beta-casein, eIF-2, and eIF-3; the extent of stimulation was dependent on the affinity for casein kinase II and the level of the substrate. These effects were observed in the range of glycerate-2,3-P2 concentrations predicted for intracellular fluctuations in this metabolite. Therefore, it was concluded that glycerate-2,3-P2 could function both as an activator and an inhibitor of casein kinase II in the erythroid cell by binding at the substrate binding site.

2,3-Diphosphoglycerate↗
PubMed1984

Kinetics of activation of casein kinase II by polyamines and reversal of 2,3-bisphosphoglycerate inhibition.

The effects of polyamines on the catalytic activity of casein kinase II have been studied. Of the three polyamines tested (putrescine, spermidine, and spermine), spermine was the most effective at stimulating the enzyme. When physiological concentrations of potassium and magnesium were utilized, 50% activation was observed at 0.28 mM spermine or 0.70 mM spermidine. With mixtures of spermine and spermidine at physiological concentrations for the reticulocyte (0.04 and 1.06 mM, respectively), a 2.5-fold stimulation of casein kinase II activity was observed. In general, stimulation of the enzyme was dependent on salt concentration and it was necessary to hold ionic strength constant in order to separate specific activation by the polyamines from general salt activation. Optimum activation by polyamines was observed at low ionic strength and physiological concentrations of Mg2+. When beta-casein and eukaryotic initiation factors 2 or 3 were used as substrates, up to 3.5-fold stimulation of casein kinase II was observed. In the absence of polyamine, half-saturation of the enzyme by Mg2+ was observed at 1-3 mM MgCl2, a concentration much higher than required for ATP-Mg2+ complex formation. This dependence of the enzyme on Mg2+ was greatly diminished in the presence of spermine. Spermine decreased the apparent Km for casein and increased the maximum velocity of the reaction. Spermidine and spermine also effectively reversed inhibition by 2,3-bisphosphoglycerate. The significant activation by polyamines observed under conditions similar to those measured for the red cell suggest that the polyamines, spermidine and to a lesser extent spermine, function to regulate casein kinase II in vivo.

2,3-Diphosphoglycerate↗
PubMedDate not supplied

[Experimental data on milk casein absorption into the blood in the early postnatal period of development].

Blood absorption of unchanged molecules of the food protein casein was studied. Of 18 test serum samples withdrawn from portal blood of a satiated lamb, only 8 contained casein-like protein that had an immunoelectrophoretic mobility of casein and provided a reaction identical to that of casein preparation. Casein hydrolysis products did not interact with anticasein serum. The evidence obtained warrants the conclusion that under normal physiological conditions an insignificant part of casein may be absorbed unchanged by blood from the intestinal lumen during the early postnatal development.

Absorption↗
PubMedDate not supplied

Evaluation of lymphocyte proliferative responses to casein hydrolysate formula in cow's milk-sensitive children: response of peripheral blood mononuclear cells to hydrolysate formula.

The proliferative responses of peripheral blood mononuclear cells (PBMCs) to cow's milk proteins and a casein hydrolysate formula were investigated in 10 cow's milk-sensitive patients. The casein hydrolysate formula reduced the symptoms in seven children but not in three. The proliferative responses of PBMCs to cow's milk proteins and the formula were higher in the three patients whose symptoms were not reduced by casein hydrolysate formula. However, the proliferative responses of PBMCs to hydrolysate formula were lower than those to cow's milk proteins in patients whose symptoms were reduced by casein hydrolysate formula. These results suggest that an elimination diet with casein hydrolysate formula may not be as effective in some patients with cow's milk allergy whose PBMCs proliferate to casein hydrolysate formula.

Caseins↗
PubMed1994

Effect of addition of brewer's yeast to soy protein and casein on plasma cholesterol levels of rabbits.

The purpose of this study was to determine whether the addition of high levels of yeast to casein and soy diets could modify the well known effects of any of these proteins on plasma cholesterol. Rabbits, were fed either a diet containing soybean protein-brewer's yeast or casein-brewer's yeast (each protein source providing 50 percent of the dietary nitrogen content) and casein and soybean protein basal diets. Brewer's yeast was obtained from a local beer factory in its non-debittered form. The diets contained 20 percent protein, 9 percent coconut oil and 1 percent corn oil, with no added cholesterol. After a 22 day experimental period, rabbits fed casein developed hypercholesterolemia whereas those fed the soybean protein diet did not. The replacement of 50 percent of the soy nitrogen by brewer's yeast nitrogen, increased the total cholesterol plasma level, but significant differences were only observed between rabbits fed casein and casein-yeast and those fed soybean protein. No differences in high density lipoprotein cholesterol could be detected among the groups. However, the HDL-cholesterol/total cholesterol ratio was significantly reduced in response to soy substitution by brewer's yeast. The (low density lipoprotein + very low density lipoprotein)--cholesterol was increased in all groups with the exception of the animals fed purely soy protein. These data suggest a hypercholesterolemic activity of the dietary non-debittered brewer's yeast. Nevertheless, according to the amino acid composition, the factor responsible for the reported effects of dietary yeast was not associated with a high lysine to arginine ratio which could be due to extracellular components.

Animals↗
PubMed1994

[Behavior of iron fixed on bovine and phosphorylated casein after hydrolysis produced by digestive proteases].

The phosphate groups of the native and phosphorylated casein have the property of sequestering the iron. This metal fixation depends on the casein's degree of phosphorylation. The phosphate groups either, naturally present or chemically binded, are the preferential fixation sites for iron. They modify the affinity constant of the casein respecto to iron. Both, phosphorylation and ironfixation influence negatibily the caseins sensibility to digestive protease. Whichever the enzyme might be, the hydrolysis of the casein with fixed iron produces fixed iron peptides. It seems that iron retention is a function of the number of phosphate groups associated to casein.

Animals↗
PubMed1994

Modes of regulation of casein kinase II.

Casein kinase II is unique when compared to other protein kinases; it utilizes GTP with almost the same effectiveness as ATP and exists as an active holoenzyme which does not need to be activated by dissociation of regulatory subunits or unfolding of regulatory domains. In vitro, the activity of casein kinase II is inhibited by acidic compounds and stimulated by basic compounds. Casein kinase II activity is inhibited by 2,3-bisphosphoglycerate and stimulated by polyamines at levels which are physiological in red cells. To examine the effects of autophosphorylation of the beta subunit on activity, two mutants of the Drosophila beta subunit have been constructed in which Ser-4 or Ser-(2-4) are changed to alanine residues. Analysis of autophosphorylation with wild-type and mutant recombinant holoenzymes reveals Ser-2 and Ser-3 as the major autophosphorylation sites. Autophosphorylation does not affect the phosphorylation of casein, but reduces the rate of phosphorylation of glycogen synthase by 30%, elongation factor I by 50-70%, and calmodulin by 20-40%. The data indicate that autophosphorylation of the beta subunit can negatively regulate the phosphotransferase activity of casein kinase II with physiological substrates. To examine regulation of casein kinase II activity by the beta subunit, recombinant alpha and beta subunits from human and Drosophila were expressed in Escherichia coli. Upon formation of the holoenzyme, the beta subunit stimulated the catalytic activity 4- to 5-fold. The catalytic alpha subunit contains the eleven conserved subdomains characteristic of all protein kinases.(ABSTRACT TRUNCATED AT 250 WORDS)

2,3-Diphosphoglycerate↗
PubMed1993

DNA topoisomerase II and casein kinase II associate in a molecular complex that is catalytically active.

Immunoprecipitation of DNA topoisomerase II from yeast results in a preparation that contains casein kinase II; this suggests that the two proteins may associate in the intact cell. Purified recombinant topoisomerase II and casein kinase II associate to form a complex in vitro which is stable after topoisomerase II becomes phosphorylated by the kinase. Studies with isolated recombinant casein kinase II subunits disclosed that although the alpha (catalytic) subunit alone can efficiently phosphorylate topoisomerase II, the formation of a stable topoisomerase II-casein kinase II association requires the presence of the beta subunit of the kinase. Both proteins engaged in this complex retain their catalytic activities. Naturally occurring polyamines and polyanionic compounds appear to be crucial factors governing the interaction between the two proteins. Although the biological significance of a stable catalytically active topoisomerase II-casein kinase II molecular complex remains to be defined, these observations suggest the possibility of a novel mechanism regulating topoisomerase II and casein kinase II activities.

Amino Acid Sequence↗