Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P47989 (xanthine oxidase)
 8,633 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cytoplasm from lactating cells is included with some milk fat globules at secretion. The objective was to search for factors causing this phenomenon. Globules bearing crescents of cytoplasm were selectively stained with the fluorescent dye, acridine orange, and their proportion in the globule population was obtained by counting from photomicrographs. Incidence of crescents on fat globules in milk samples of 50 human donors ranged from 1 to 29%, and the mean was 7.2%. Two bovine milk samples, both representing over 100 animals, contained 1% or less of globules with crescents. Globules in individual milkings of five beef cows showed the same low proportion of crescents. In addition to species, genetic and diurnal factors influenced numbers of crescents. Two sisters showed evidence within and between lactations of a persistent high proportion (greater than 25%) of globules with crescents. Samples collected in the a.m. contained a lower percentage of globules with crescents (6.5%) than those obtained in the p.m. (9.7%). Crescent incidence was not correlated with lipid or protein content of human milk, interval within a milking, days in lactation, or the donor's age. Evidence is presented to suggest that the concentration, distribution, and acylation of butyrophilin and xanthine oxidase, coat proteins of the apical plasma membrane, are important factors in globule crescent formation.
 ...
PMID:Factors related to the formation of cytoplasmic crescents on milk fat globules. 212 8

1. N-glycanase, but not O-glycanase, released carbohydrates from butyrophilin of rat and cow milk lipid globule membranes. 2. 1-Deoxynojirimycin, and inhibitor of glucosidases I and II of the glycoprotein processing pathway, increased the amount or extent of glycosylation of butyrophilin in rat milk lipid globules. 3. Butyrophilin and xanthine oxidase of milk lipid globule membrane had a nearest neighbor relationship, as demonstrated through specific crosslinking of these proteins. 4. From these results it is suggested that butyrophilin has asparagine-linked oligosaccharides which bypass the processing apparatus of endoplasmic reticulum and Golgi apparatus. Butyrophilin may be responsible for anchoring xanthine oxidase to the inner (cytoplasmic) face of milk lipid globule membrane.
 ...
PMID:Butyrophilin of milk lipid globule membrane contains N-linked carbohydrates and cross-links with xanthine oxidase. 252 60

Differential scanning calorimetry of bovine milk fat globule membranes (MFGM) yields five to eight transitions, depending on the conditions employed during isolation and assay of the membranes. Transitions A, B, and C were shown in a previous publication to derive from lipid melting, while transition D was found to stem from the unfolding of a structural protein termed butyrophilin [K. C. Appell, T. W. Kennan, and P. S. Low (1982) Biochim. Biophys. Acta 690, 243-250]. In this report we present evidence that the E1, E2, and F endotherms derive from the major MFGM protein, xanthine oxidase. Support for this contention derives from (i) thermal gel analysis; (ii) thermal inactivation analysis; (iii) comparison of the calorimetric properties of endotherms I, II, and III of purified xanthine oxidase with transitions E1, E2, and F of MFGM; (iv) comparison of the properties of a peculiar exotherm in scans of both the purified enzyme and MFGM; and (v) examination of the effects of specific ligands, reducing agents, and pH on both the xanthine oxidase and MFGM transition. The existence of three independent endotherms (I, II, and III) in purified xanthine oxidase demonstrates that the enzyme is composed of multiple independent domains. The interconversion of transitions I (E1) and II (E2) with a change in the redox conditions of the medium implies that these two transitions may be manifestations of the interconvertible dehydrogenase and oxidase forms of the enzyme, respectively. The relative independence of the I/II transitions from transition III further shows that only slight interaction between the major domains of xanthine oxidase exists.
 ...
PMID:Identification and partial characterization of the xanthine oxidase transitions of the milk fat globule membrane. 383 55

The milk-fat-globule membrane (MFGM) was isolated from guinea-pig milk and the membrane-associated proteins and glycoproteins characterized by electrophoretic techniques. Major components of the membrane included PAS-I, a sialoglycoprotein of Mr greater than or equal to 200000, the redox enzyme xanthine oxidase and the glycoprotein, butyrophilin. Membrane preparations also contained two other glycoproteins, GP-80 and GP-55, of Mr 80000 and 55000, respectively. Comparison of guinea-pig xanthine oxidase and butyrophilin with proteins from bovine MFGM by peptide mapping procedures, showed that the two proteins in both species were similar, but not identical. GP-55 may also be related to glycoproteins of Mr 45000 and 48000 in the bovine membrane. The integral and peripheral components of guinea-pig MFGM were identified by treating membrane preparations with sodium carbonate solutions at high pH and by partitioning the membrane proteins in solutions of Triton X-114. By these criteria xanthine oxidase and GP-55 appeared to be peripheral components and GP-80 an integral protein of the membrane. PAS-I and butyrophilin displayed hydrophilic properties in Triton X-114 solutions, but could not be removed from membrane preparations with sodium carbonate. Possible reasons for these ambiguous data are discussed. The observed similarity between several of the proteins of guinea-pig and bovine MFGM implies that these proteins may have specific functions related to milk secretion in mammary tissue, e.g. in the budding of milk-fat globules or the exocytosis of milk protein and lactose at the apical surface.
 ...
PMID:Identification and characterization of the principal proteins of the fat-globule membrane from guinea-pig milk. 402 34

Guinea-pig mammary tissue was perfused in vitro, radiolabelled with [35S]methionine and intracellular protein precursors of the milk-fat-globule membrane (FGM) recovered by immunoabsorption techniques. Labelled xanthine oxidase was solely detected in post-microsomal supernatants and butyrophilin in carbonate-washed membranes. A major glycoprotein (Gp 55), was initially present in a membrane-bound form, but after longer perfusion times a fraction of this protein was recovered in the post-microsomal supernatant. These results are discussed with reference to formation of the apically-derived FGM.
 ...
PMID:Protein synthesis in lactating guinea-pig mammary tissue perfused in vitro. II. Biogenesis of milk-fat-globule membrane proteins. 653 41

The proteinaceous coat associated with the cytoplasmic side of milk lipid globule membranes (MLGM) was prepared from bovine and caprine milk by removal of membrane material with non-ionic detergent. These coat preparations, which were enriched in two major proteins, a glycoprotein of polypeptide M, 67 000 (butyrophilin) and a non-glycosylated protein of polypeptide Mr 155 000 (xanthine oxidase), contained small amounts of fatty acids which could not be removed by exhaustive extractions with organic solvents. Both butyrophilin and xanthine oxidase of bovine MLGM were excised and eluted from SDS-polyacrylamide gels and were shown to contain 1 to 2 moles of bound fatty acids per mole of protein. Palmitic, stearic and oleic acids were the predominant protein-bound fatty acids, but no specificity for binding of individual fatty acids was observed. The fatty acids were not rendered soluble in organic solvents when the protein preparations were incubated with phospholipases A or C or with trypsin. Treatment with 0.25 M NaOH at 100 degrees C for 1 h or with 1 M hydroxylamine at 4 degrees C for 16 h, however, released virtually all of the fatty acids associated with these proteins. Similar results were obtained with two major proteins, bands 3 and 4.1, or rat erythrocyte plasma membrane. By contrast, skeletal muscle actin and serum albumin had no bound fatty acids that could be released by alkali treatment. These results show that fatty acids are bound to a number of membrane-associated proteins, both glycosylated and unglycosylated, via linkages that resist purification of the proteins on SDS-polyacrylamide gel electrophoresis and are suggestive of covalent attachment of fatty acids to these proteins. The possible involvement of this acylation in processes characterized by local changes of membrane shape and plasticity is discussed.
 ...
PMID:Tight attachment of fatty acids to proteins associated with milk lipid globule membrane. 706 4

A cDNA encoding mouse butyrophilin was obtained by reverse transcriptase-coupled polymerase chain reaction (RT-PCR) using poly (A)+ RNA from lactating mouse mammary gland as a template and screening a cDNA library with the RT-PCR-amplified fragment as a probe. DNA sequencing and computer analysis revealed that it has a rather long 3'-untranslated sequence and that the carboxy-terminal cytoplasmic domain was well conserved between mouse and bovine butyrophilins. To elucidate the biological function of butyrophilin, the cytoplasmic region expressed as fusion protein with glutathione S-transferase (GST) was purified and incubated with the cell lysate of mouse mammary epithelial cell lines, COMMA-ID and HC11. A 150-kDa protein was shown to specifically associate with the cytoplasmic domain and the protein increased in amount when the cells were treated with basal medium supplemented with lactogenic hormones such as prolactin, insulin and glucocorticoid. N-terminal amino acid sequencing indicated that the protein is xanthine dehydrogenase/oxidase which has been cloned from mouse liver. Further, the cytoplasmic domain also bound xanthine dehydrogenase/oxidase from bovine milk fat globule membrane. These results suggest that butyrophilin might be physiologically associated with xanthine dehydrogenase/oxidase and might function in a complex form in milk fat secretion.
 ...
PMID:Carboxy-terminal cytoplasmic domain of mouse butyrophilin specifically associates with a 150-kDa protein of mammary epithelial cells and milk fat globule membrane. 854 2

Milk lipid globules from humans, cows and rats contained a protein identified as adipocyte differentiation-related protein (ADRP) associated with the globule surface membrane material. This protein, previously believed to be specific to adipocytes, was a major constituent of the globule surface and was present in a detergent-insoluble complex that contained stoichiometric amounts of butyrophilin and xanthine oxidase. Identification of ADRP was by sequence similarity of tryptic peptides from cow and human proteins with the sequence inferred from the cDNA for mouse ADRP. The putative ADRP of lipid globules from cow, human and rat milk was recognized specifically by antisera raised against a peptide synthesized to duplicate the N-terminal 26 residues of the mouse protein. In homogenates of lactating mammary gland, ADRP was found only in endoplasmic reticulum and in lipid droplet fractions. ADRP was modified, apparently post-translationally, and one modification apparently was acylation, primarily with C14, C16 and C18 fatty acids. Two isoelectric variants of ADRP were present in cow globule membrane material. In vitro, ADRP served as a substrate for protein kinases associated with milk lipid globule membrane, but this protein did not seem to become phosphorylated intracellularly.
 ...
PMID:Adipocyte differentiation-related protein is secreted into milk as a constituent of milk lipid globule membrane. 900 95

We investigated the expression of butyrophilin in eukaryotic cells with a view to determining the number of mRNA species, the incorporation of the peptide chain into microsomes, and the topology of the processed protein in biological membranes. Butyrophilin is synthesized from a single sized mRNA in both bovine and murine lactating mammary tissue and associates with microsomal membranes with a type I topology (Nexo.Ccyto) via a single hydrophobic anchor in the middle of the sequence. Several isoelectric variants of the protein were detected in cellular membranes from lactating bovine mammary tissue and in the milk-fat-globule membrane. We found no evidence for soluble forms of butyrophilin in postmicrosomal supernatants. The 66-kDa protein appears to be subjected to limited proteolysis, giving rise to a 62-kDa fragment lacking the C terminus and to other more minor fragments of lower Mr in the milk-fat-globule membrane. Antipeptide antibodies to epitopes within the N- and C-terminal domains were used to show that butyrophilin retains a type I topology in plasma membranes when expressed in insect cells from a baculovirus vector, and in secreted milk-fat globules. These data do not agree with previous suggestions that butyrophilin may exist in cytoplasmic soluble forms, or be reorganized in the plane of the lipid bilayer during secretion in lipid droplets from mammary cells. The results are discussed with reference to the role butyrophilin may play as the principal scaffold for the assembly of a complex with xanthine oxidase and other proteins that functions in the budding and release of milk-fat globules from the apical surface during lactation.
 ...
PMID:Butyrophilin is expressed in mammary epithelial cells from a single-sized messenger RNA as a type I membrane glycoprotein. 946 13

The characteristics and possible functions of the most abundant proteins associated with the bovine milk-fat globule membrane are reviewed. Under the auspices of the Milk Protein Nomenclature Committee of the ADSA, a revised nomenclature for the major membrane proteins is proposed and discussed in relation to earlier schemes. We recommend that proteins be assigned specific names as they are identified by molecular cloning and sequencing techniques. The practice of identifying proteins according to their Mr, electrophoretic mobility, or staining characteristics should be discontinued, except for uncharacterized proteins. The properties and amino acid sequences of the following proteins are discussed in detail: MUC1, xanthine dehydrogenase/oxidase, CD36, butyrophilin, adipophilin, periodic acid Schiff 6/7 (PAS 6/7), and fatty acid binding protein. In addition, a compilation of less abundant proteins associated with the bovine milk-fat globule membrane is presented.
 ...
PMID:A review and proposed nomenclature for major proteins of the milk-fat globule membrane. 1071 56


1 2 3 Next >>