Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.17.3.2 (xanthine oxidase)
 8,383 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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.
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PMID:Butyrophilin of milk lipid globule membrane contains N-linked carbohydrates and cross-links with xanthine oxidase. 252 60

Part of the fatty acid synthase in cytosol from mammary glands of lactating rats was in a complex with other proteins and with lipids. This complex eluted in the void volume from a gel filtration column with an exclusion limit of 5,000,000, and remained in a 3% polyacrylamide stacking gel during electrophoresis under nondenaturing conditions. Fatty acid synthase-containing lipoprotein particles ranged in density from 1.07 to 1.16 g/ml, and varied in protein to lipid ratios. Similar fatty acid synthase particles were present also in cytosol from cow mammary gland. Butyrophilin, xanthine oxidase, and a group of small GTP-binding proteins that included ADP-ribosylation factor, were identified as constituents of the lipoprotein complex. This complex interacted with endoplasmic reticulum and with lipid droplets in cell-free incubation mixtures. In ultrastructure fatty acid synthase-containing lipoprotein particles were homogeneous in appearance, but were heterogeneous in size, with apparent diameters of 40 to 170 nm. Immunocytochemically, antigen recognized by antibodies to fatty acid synthase were found to be present in these particles and on endoplasmic reticulum. Lipoprotein complexes bound to specific polypeptides of endoplasmic reticulum.
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PMID:Cytosolic lipoprotein particles from milk-secreting cells contain fatty acid synthase and interact with endoplasmic reticulum. 781 19

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.
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PMID:Butyrophilin is expressed in mammary epithelial cells from a single-sized messenger RNA as a type I membrane glycoprotein. 946 13

Butyrophilin 1A1 (BTN1A1) and xanthine oxidoreductase (XOR) are highly expressed in the lactating mammary gland and are secreted into milk associated with the milk fat globule membrane (MFGM). Ablation of the genes encoding either protein causes severe defects in the secretion of milk lipid droplets, suggesting that the two proteins may function in the same pathway. Therefore, we determined whether BTN1A1 and XOR directly interact using protein binding assays, surface plasmon resonance analysis, and gel filtration. Bovine XOR bound with high affinity in a pH- and salt-sensitive manner (KD=101+/-31 nM in 10 mM HEPES, 150 mM NaCl, pH 7.4) to the PRY/SPRY/B30.2 domain in the cytoplasmic region of bovine BTN1A1. Binding was stoichiometric, with one XOR dimer binding to either two BTN1A1 monomers or one dimer. XOR bound to BTN1A1 orthologs from mice, humans, or cows but not to the cytoplasmic domains of the closely related human paralogs, BTN2A1 or BTN3A1, or to the B30.2 domain of human RoRet (TRIM 38), a protein in the TRIM family. Analysis of the protein composition of the MFGM of wild type and BTN1A1 null mice showed that most of the XOR in mice lacking BTN1A1 was released from the MFGM in a soluble form when the milk lipid droplets were disrupted to prepare membrane, compared with wild-type mice, in which most of the XOR remained membrane-bound. Thus BTN1A1 functions in vivo to stabilize the association of XOR with the MFGM by direct interactions through the PRY/SPRY/B30.2 domain. The potential significance of BTN1A1/XOR interactions in the mammary gland and other tissues is discussed.
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PMID:The PRY/SPRY/B30.2 domain of butyrophilin 1A1 (BTN1A1) binds to xanthine oxidoreductase: implications for the function of BTN1A1 in the mammary gland and other tissues. 1953 72