SEARCH · PubMed Health

Results for “LACTOGLOBULINS”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7Linked to original sources

PubMed2004

Interfacial and molecular properties of high-pressure-treated beta-lactoglobulin B.

Interfacial properties of beta-lactoglobulin B subjected to hydrostatic pressures up to 400 MPa were studied by measuring surface pressure at the air/water interface and the elastic interfacial shear modulus at the oil/water interface. The surface hydrophobicity of pressurized beta-lactoglobulin was determined by an 1-anilino-naphthalene-8-sulfonate assay and exposure of free thiol groups using the Ellman assay. The molar mass of pressure-induced oligomers was measured using a combination of size exclusion chromatography, light scattering, and refractive index measurements. High-pressure treatment of beta-lactoglobulin increased the surface pressure growth rate and its final level at the air/water interface. After high-pressure treatment, the maximum interfacial elasticity at the oil/water interface increased, and the time lag before growth of the interfacial elasticity decreased. Up to 200 MPa, large amounts of monomeric beta-lactoglobulin were formed with increased exposure of thiol groups and increased surface hydrophobicity compared to unpressurized beta-lactoglobulin. At a pressure higher than 200 MPa, surface hydrophobicity continued to increase, while exposure of thiol groups decreased, the latter due to the formation of covalently linked oligomers. We have shown that surface hydrophobicity rather than thiol exposure is important for the pressure-induced increase in growth rate and the final level of surface pressure at the air/water interface and in interfacial elasticity at the oil/water interface.

Anilino Naphthalenesulfonates↗

PubMed2001

Lamina propria lymphocytes produce interferon-gamma and develop suppressor activity in response to lactoglobulin.

This study examines the in vitro response of human lamina propria lymphocytes (LPLs) to food antigens. LPLs were obtained from jejunum of healthy individuals undergoing gastric bypass operations for morbid obesity. Proliferation was assayed by [3H]thymidine incorporation and cytokine production by ELISA. LPLs proliferated in response to keyhole limpet hemocyanin, ovalbumin, lactoglobulin, and phytohemagglutinin (PHA), but not to yeast. The responses to lactoglobulin and PHA were inhibited by the CTLA4/Fc chimera and by MAbs against CD2, CD58, CD80, and CD86, indicating stimulation of CD28+ LPLs with antigen-presenting cells through activation of the CD2 pathway. Besides producing IL-2, IL-10, and TNF-alpha, LPLs synthesized large amounts of IFN-gamma (100 ng/ml) with lactoglobulin, a process dependent upon CD80/CD86, CD40/CD40L, and IL-12. After a three-day culture with lactoglobulin, ovalbumin, or PHA, LPLs developed suppressor activity that reduced proliferation of naive LPLs to these same stimuli. In summary, LPLs first respond to lactoglobulin by proliferation and IFN-gamma production, then by development of antigen nonspecific suppression.

Cell Division↗

PubMed1996

Expression and secretion of recombinant ovine beta-lactoglobulin in Saccharomyces cerevisiae and Kluyveromyces lactis.

High expression and secretion of recombinant ovine beta-lactoglobulin has been achieved in the yeast Kluyveromyces lactis. The yield of beta-lactoglobulin is 40-50 mg per litre of culture supernatant and accounts for approx. 72% of the total secreted protein. Constitutive expression is under the control of the Saccharomyces cerevisiae phosphoglycerate kinase promoter from an intronless version of the beta-lactoglobulin gene. Secretion is specified by the ovine protein's own signal sequence. this system, coupled to an efficient and novel recovery protocol, allows 30 mg of pure protein to be isolated from a typical 1 litre culture. The protein is virtually indistinguishable from beta-lactoglobulin conventionally purified from sheep milk by its behaviour in native PAGE and SDS/PAGE, reactivity to antibodies, CD, fluorescence spectroscopy and N-terminal sequencing. Attempts to achieve a similar expression and secretion system in the yeast S. cerevisiae met with only limited success, although it was found that heat-shock treatment modestly increased the yield up to approx. 3-4 mg per litre of culture supernatant. Site-directed mutagenesis showed that secretion in S. cerevisiae depended upon correct formation of the two disulphide bonds present in beta-lactoglobulin.

Amino Acid Sequence↗

PubMed2001

Dimerization, stability and electrostatic properties of porcine beta-lactoglobulin.

The study of homologous proteins belonging to the same family can provide a rationale for important molecular properties such as oligomer formation, folding mechanism and mode of binding. We report here a physico-chemical characterization of porcine beta-lactoglobulin, purified from pooled milk: size-exclusion chromatography, CD and NMR measurements were used to study the aggregation and stability of this protein. In spite of the high sequence identity and homology of porcine beta-lactoglobulin with the widely studied bovine species, the two proteins exhibit very different behaviours. The porcine protein shows a monomer-dimer equilibrium with a pH dependence opposite to that observed for the bovine species. Unfolding experiments revealed the presence of an intermediate that probably has excess alpha helices, as reported for equine species. Modelling studies were performed on bovine, porcine and equine proteins, and, interestingly, electrostatic surface potential calculations led to results consistent with the different dimer interface found for porcine beta-lactoglobulin in the crystal structure. Interaction studies revealed that porcine beta-lactoglobulin is unable to bind fatty acids at any pH, thus questioning the main functional role proposed for lactoglobulins as fatty acid transporters or solubilizers.

Amino Acid Sequence↗

PubMed2000

Detection of IgA antibodies to cat, beta-lactoglobulin, and ovalbumin allergens in human milk.

BACKGROUND: The relationship between the development of allergy during infancy and breast-feeding remains controversial. This controversy may be due to individual variations in the composition of human milk. Antibodies to food antigens to which the mother is commonly exposed are present in the milk, but their relationship to allergy is still unknown. IgA antibodies to inhalant allergens have not been previously detected. OBJECTIVE: Our purpose was to analyze secretory IgA antibody levels to cat, beta-lactoglobulin, and ovalbumin allergens in colostrum and mature milk in relation to maternal allergy. METHODS: Colostrum and samples of mature milk were obtained after 1 and 3 months of lactation from 53 nursing mothers (17 allergic and 36 nonallergic mothers) and were analyzed for total secretory IgA levels by ELISA and secretory IgA antibodies to cat, beta-lactoglobulin, and ovalbumin by an enzyme-amplified ELISA. The specificity of the assays was confirmed by inhibition experiments. RESULTS: Secretory IgA to cat, beta-lactoglobulin, and ovalbumin allergens were detected in colostrum as well as mature milk. The levels of secretory IgA to ovalbumin were lower in colostrum from allergic mothers with P =.016, whereas the levels to beta-lactoglobulin and cat were similar in the 2 groups. IgA antibodies to ovalbumin were detected in 94% of the colostrum samples from allergic and in all samples from nonallergic mothers, in 82% and 96%, respectively at 1 month, and 53% and 65% at 3 months. Fewer samples had detectable secretory IgA antibodies to beta-lactoglobulin than to ovalbumin and cat, and only 33% and 10% of the samples from the allergic and nonallergic mothers, respectively, remained positive at 3 months. All the allergic mothers had detectable IgA to cat in colostrum, whereas 83% and 73% of the samples were positive at 1 and 3 months. The corresponding numbers were 93%, 81%, and 81% in the nonallergic mothers (not significant). CONCLUSION: Even a low level of exposure of the mucosa (eg, by inhalant allergens) can induce antibody secretion into the milk, both in allergic and nonallergic mothers.

Allergens↗

PubMed1991

Multiple forms of mRNA encoding human pregnancy-associated endometrial alpha 2-globulin, a beta-lactoglobulin homologue.

Human pregnancy-associated endometrial alpha 2-globulin (alpha 2-PEG) is the major secretory protein product of the endometrium during embryo implantation and the first few weeks of pregnancy. It is a homologue of beta-lactoglobulin, a retinol binding protein, but unlike beta-lactoglobulin it is not found in the mammary gland. The cloning and sequencing of 34 alpha 2-PEG clones has revealed several minor variant forms indicative of alternatively spliced alpha 2-PEG pre-mRNA. These minor forms have also been detected amongst uncloned cDNA after PCR amplification. Some of these mRNAs would give rise to forms of alpha 2-PEG protein lacking internal sequences, whereas others affect the mRNA sequences on the 3' boundary of the presumed termination codon. Sequences within the cDNA clones are consistent with the existence of splice sites, and together with similarities found between alpha 2-PEG cDNA and beta-lactoglobulin gene sequences there is good evidence in support of an unusual scheme for the alternative splicing of alpha 2-PEG pre-mRNA involving both alternative 5' splice sites and alternative 3' splice sites. This scheme suggests that the alpha 2-PEG and beta-lactoglobulin genes share a similar structure in at least two regions, and it is likely that beta-lactoglobulin pre-mRNA would show a similar pattern of alternative splicing for one of these regions.

Amino Acid Sequence↗

PubMed1998

Adhesion inhibitory activity of beta-lactoglobulin isolated from infant formulae.

Beta-lactoglobulin was isolated from infant formulae that were ultra high temperature (UHT) -treated, sterilized or spray-dried. The effect of the isolated beta-lactoglobulin on SfaII-fimbriae-mediated adhesion of Escherichia coli to human ileostomy glycoproteins was studied in vitro. Beta-lactoglobulin isolated from sterilized formulae was found to perform significantly less well than preparations from spray-dried formulae (p = 0.05). Great heterogeneity was observed in the adhesion inhibitory capacity of beta-lactoglobulin isolated from UHT-treated formulae. Therefore, no significant difference was observed between UHT-treated and sterilized formulae or spray-dried formulae (p > 0.10). It can be hypothesized that beta-lactoglobulin from spray-dried and some UHT-treated infant formulae may affect the colonization of mucous membranes by E. coli strains causing neonatal septicaemia and meningitis.

Bacterial Adhesion↗

PubMedDate not supplied

Human milk components cross-reacting with antibodies against bovine beta-lactoglobulin.

The human whey components cross-reacting with antibodies raised against bovine and/or equine beta-lactoglobulin were screened systematically. The milk of six women on a normal diet was collected within 72 h of confinement and whey components were fractionated by high-speed size exclusion chromatography and reversed-phase techniques. The fractions which were immunoreactive in double diffusion experiments with antisera anti-bovine and/or equine beta-lactoglobulin were subsequently purified by native PAGE and then electroblotted on Pro-blott membrane (Western blotting). Pro-blot membranes were stained in parallel with Coomassie and by immunostaining using antibodies against bovine and/or equine beta-lactoglobulin as first antibody solution. The immunoreactive bands were cut out from the membrane and N-terminally sequenced; all the immunoreactive components were clearly identified as human beta-casein or its (mainly tryptic) fragments. The strong antigenic similarity between human beta-casein and beta-lactoglobulin (bovine and equine) might be of immunological importance; it could mean that breast-fed neonates risk being sensitized to beta-lactoglobulin irrespective of the presence of cow's milk in the mother's diet.

Amino Acid Sequence↗

PubMed1998

Sensitive enzyme immunoassay for anti-beta-lactoglobulin IgG in serum.

A sensitive enzyme immunoassay for anti-beta-lactoglobulin immunoglobulin G (IgG) in serum is described. Serum containing anti-beta-lactoglobulin IgG was reacted simultaneously with 2,4-dinitrophenyl-bovine serum albumin-beta-lactoglobulin conjugate and beta-lactoglobulin-peroxidase conjugate. The complex formed from the three components was trapped onto polystyrene balls coated with anti-2,4-dinitrophenyl group IgG, eluted with epsilon N-2,4-dinitrophenyl-L-lysine and transferred to polystyrene balls coated with anti-human IgG.gamma-chain IgG. Bound peroxidase activity was determined by fluorometry. This enzyme immunoassay was 100- to 1000-fold more sensitive and more reliable than the enzyme-linked immunosorbent assay (ELISA). Anti-beta-lactoglobulin IgG was detected in 91% of healthy subjects using this method.

Antibodies↗

PubMed1987

Amino acid sequence homology between human placental protein 14 and beta-lactoglobulins from various species.

The primary structure of 22 N-terminal amino acid residues of placental protein 14 was determined by automated Edman degradation with a gas-phase sequencer. This protein, isolated from the human placenta and its membranes, was considered pure as evidenced by a single N-terminal amino acid sequence M D I P Q T K Q D L E L P K L A G T W H S M. It shows significant sequence homology with horse, bovine, buffalo, sheep and goat beta-lactoglobulins. We found 13 identities out of 22 possible matches with horse beta-lactoglobulin. beta-lactoglobulins from several animal species have been found to bind retinol. Among the identical residues there is one tryptophan at position 19 which is conserved in beta-lactoglobulins and is also found in the human retinol-binding protein at the corresponding position. These data suggest a common origin of PP14 and beta-lactoglobulins.

Amino Acid Sequence↗

PubMed1987

The complete amino-acid sequence of dimeric beta-lactoglobulin from mouflon (Ovis ammon musimon) milk.

beta-Lactoglobulin from Mouflon (Ovis ammon musimon) milk has been isolated and its complete primary structure determined. This protein has been isolated in dimeric form and has a molecular mass of 37 kDa. The amino-acid sequence has been determined by microsequencing of the native protein and the peptides were obtained after tryptic cleavage. The tryptic peptides were isolated by reversed phase high-performance liquid chromatography. The primary structure of mouflon beta-lactoglobulin shows close similarity to ruminant beta-lactoglobulins. The presence of His at position 20 indicates that this protein belongs to the B-type of dimeric ovine beta-lactoglobulins. Mouflon beta-lactoglobulin is a 162 amino acid long polypeptide chain with two disulphide bridges and one free thiol group. Structural similarities to the bilin-binding protein, BG protein from olfactory epithelium and retinol-binding protein are discussed.

Amino Acid Sequence↗

PubMed1988

Microanalysis of the amino-acid sequence of monomeric beta-lactoglobulin I from donkey (Equus asinus) milk. The primary structure and its homology with a superfamily of hydrophobic molecule transporters.

The complete primary structure of donkey beta-lactoglobulin I was determined by pulsed-liquid phase microsequencing of tryptic peptides. The protein has been isolated in monomeric form and it corresponds to monomeric beta-lactoglobulin of type I. With the inclusion of donkey beta-lactoglobulin I there are 13% common residues amongst the members of the beta-lactoglobulin family. Donkey beta-lactoglobulin I is homologous to the retinol-binding protein, bilin-binding protein and five other proteins belonging to the new superfamily of hydrophobic molecule transporters. A rapid method for peptide isolation and the strategy for microsequencing of this protein have been described.

Amino Acid Sequence↗

PubMed1985

Selected functionality changes of beta-lactoglobulin upon esterification of side-chain carboxyl groups.

Free carboxyl groups of bovine beta-lactoglobulin were esterified with methanol, ethanol, and n-butanol. The modified proteins showed increased positive charge as the number of ionizable carboxyl groups was reduced. The methyl, ethyl, and butyl esters of beta-lactoglobulin showed enhanced surface activity, determined with surface and interfacial tension measurements at an air/water and oil/water interface, respectively. The methyl ester showed the largest enhancement in surface activity relative to the native protein. The ethyl and butyl esters were less effective in lowering the surface and interfacial tension but were more surface active than the native protein. The hydrophobic probe, 1,8-anilinonaphthalene sulfonate, showed enhanced fluorescence in the presence of native and modified beta-lactoglobulin. The largest enhancement in fluorescence of the hydrophobic probe was noted in the presence of the methyl ester of beta-lactoglobulin. The ethyl ester also effectively enhanced the fluorescence of the probe. The slopes of the curves of the fluorescent response for the native and modified proteins were graphically related to the interfacial tension at an oil/water interface for the corresponding protein. A large positive correlation was noted between the effectiveness of the proteins in reducing the interfacial tension and the enhancement in fluorescence of ANS with hydrophobic binding by the proteins. A general method to quantify carboxyl groups of proteins, employing the formation of a colored hydroxamate-ferric ion chelate, was also developed. Modification of the reaction for proteins in general, and carboxyl-modified proteins in particular, appears to have potential. Use of the hydroxamic acid reaction made it possible to estimate the apparent extent of carboxyl modification of beta-lactoglobulin through esterification with methanol, ethanol, and n-butanol.

Amino Acid Sequence↗

PubMed1991

Enzyme-linked immunosorbent assays for bovine alpha-lactalbumin and beta-lactoglobulin in serum and tissue culture media.

Enzyme-linked immunosorbent assays for bovine alpha-lactalbumin and beta-lactoglobulin have been developed for measurements of serum and tissue culture samples. Either alpha-lactalbumin or beta-lactoglobulin antiserum was coated on ELISA plates. Biotinylated proteins were used in competition with unknown amount of proteins in samples. After unbound proteins were washed off, ExtrAvidin-peroxidase and tetramethylbenzidine were then used as a detection system. Crossreactivity of caseins or bovine serum albumin was less than .0001% in either alpha-lactalbumin or beta-lactoglobulin ELISA. Parallel curves from serial dilutions were obtained in serum and media samples. The additivity of alpha-lactalbumin and beta-lactoglobulin ELISA was validated in either serum or medium samples. The intraassay and interassay coefficients of variation for alpha-lactalbumin and beta-lactoglobulin ELISA were below 10% over 51 and 47 assays. The ELISA are useful in mammary gland biology studies for measuring milk whey protein in serum or culture media.

Animals↗

PubMed1991

Isolation of monoclonal antibodies monospecific for bovine beta-lactoglobulin.

Monoclonal antibodies were generated against purified bovine beta-lactoglobulin A. Six antibodies reactive only with beta-lactoglobulin were selected. At least one of the antibodies appeared to be species monospecific for bovine beta-lactoglobulin. The remaining five antibodies recognized proteins in caprine and porcine whey fractions. One monoclonal antibody (59-1) exhibited a distinct 2:1 preference for beta-lactoglobulin B over A at near neutral pH (7.5). These antibodies should prove extremely useful adjuncts in structural studies of bovine beta-lactoglobulin.

Animals↗

PubMed1998

Effect of whey hydrolysate formula on the transfer of beta-lactoglobulin into serum and milk in mice.

This study was performed to elucidate the effect of whey hydrolysate formula on the transfer of an antigen into serum and milk. The concentrations of beta-lactoglobulin in serum and milk were positively correlated (p < 0.01). The concentration of beta-lactoglobulin in serum tended to become low in the mouse and to be accompanied with a high level of fecal anti-beta-lactoglobulin IgA concentration. The fecal anti-beta-lactoglobulin IgA of mice fed hydrolysate formula for 12 weeks was significantly higher than that of the control formula-fed mice (p < 0.05). These results suggest that a high level of intestinal IgA elicited by the feeding of hydrolysate formula may reduce the transfer of beta-lactoglobulin into serum and milk.

Animals↗

PubMed2000

Conformation and stability of thiol-modified bovine beta-lactoglobulin.

Bovine beta-lactoglobulin A assumes a dimeric native conformation at neutral pH, while the conformation at pH 2 is monomeric but still native. Beta-lactoglobulin A has a free thiol at Cys121, which is buried between the beta-barrel and the C-terminal major alpha-helix. This thiol group was specifically reacted with 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) in the presence of 1.0 M Gdn-HCI at pH 7.5, producing a modified beta-lactoglobulin (TNB-bIg) containing a mixed disulfide bond with 5-thio-2-nitrobenzoic acid (TNB). The conformation and stability of TNB-bIg were studied by circular dichroism (CD), tryptophan fluorescence, analytical ultracentrifugation, and one-dimensional 1H-NMR. The CD spectra of TNB-bIg indicated disordering of the native secondary structure at pH 7.5, whereas a slight increase in the alpha-helical content was observed at pH 2.0. The tryptophan fluorescence of TNB-bIg was significantly quenched compared with that of the intact protein, probably by the energy transfer to TNB. Sedimentation equilibrium analysis indicated that, at neutral pH, TNB-bIg is monomeric while the intact protein is dimeric. In contrast, at pH 2.0, both the intact beta-lactoglobulin and TNB-bIg were monomeric. The unfolding transition of TNB-bIg induced by Gdn-HCl was cooperative in both pH regions, although the degree of cooperativity was less than that of the intact protein. The 1H-NMR spectrum for TNB-bIg at pH 3.0 was native-like, whereas the spectrum at pH 7.5 was similar to that of the unfolded proteins. These results suggest that modification of the buried thiol group destabilizes the rigid hydrophobic core and the dimer interface, producing a monomeric state that is native-like at pH 2.0 but is molten globule-like at pH 7.5. Upon reducing the mixed disulfide of TNB-bIg with dithiothreitol, the intact beta-lactoglobulin was regenerated. TNB-bIg will become a useful model to analyze the conformation and stability of the intermediate of protein folding.

Animals↗

PubMedDate not supplied

[A comparative thermodynamic study of heat and cold denaturation of beta-lactoglobulin].

The changes in structure and thermodynamic parameters of beta-lactoglobulin upon heat and cold denaturation have been studied using both scanning microcalorimetry and circular dichroism spectroscopy methods. It has been shown that in contrast to the heat denaturation process, the cold denaturation of beta-lactoglobulin is accompanied by an opposite heat effect. In all cases, the calorimetrically measured enthalpy of beta-lactoglobulin cold denaturation is higher than it was expected from the two-state model of denaturation transition. It has been concluded that beta-lactoglobulin cold denaturation cannot be represented by a transition between two microscopic states--native and denatured. The latter, is due to the additional process that occurs together with the disruption of the beta-lactoglobulin tertiary structure and is accompanied by increasing heat capacity. Taking into account the heat capacity contribution of this process upon calculation of the enthalpy makes it closer to the enthalpy value calculated for the two-state model of denaturation transition.

Calorimetry, Differential Scanning↗