Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The primary amine coupling reagents succinimidyl-6-biotinamido-hexanoate (NHS-A-biotin) and sulfosuccinimidyl-6-biotinamido-hexanoate (NHS-LC-biotin) were tested for their ability to selectively label Escherichia coli cell envelope proteins in vivo. Probe localization was determined by examining membrane, periplasmic, and cytosolic protein fractions. Both hydrophobic NHS-A-biotin and hydrophilic NHS-LC-biotin were shown to preferentially label outer membrane, periplasmic, and inner membrane proteins. NHS-A- and NHS-LC-biotin were also shown to label a specific inner membrane marker protein (Tet-LacZ). Both probes, however, failed to label a cytosolic marker (the omega fragment of beta-galactosidase). The labeling procedure was also used to label E. coli cells grown in low-salt Luria broth medium supplemented with 0, 10, and 20% sucrose. Outer membrane protein A (OmpA) and OmpC were labeled by both NHS-A- and NHS-LC-biotin at all three sucrose concentrations. In contrast, OmpF was labeled by NHS-A-biotin but not by NHS-LC-biotin in media containing 0 and 10% sucrose. OmpF was not labeled by either NHS-A- or NHS-LC-biotin in E. coli cells grown in medium containing 20% sucrose. Coomassie-stained gels, however, revealed similar quantities of OmpF in E. coli cells grown at all three sucrose concentrations. These data indicate that there was a change in outer membrane structure due to increased osmolarity, which limits accessibility of NHS-A-biotin to OmpF.
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PMID:In vivo labeling of Escherichia coli cell envelope proteins with N-hydroxysuccinimide esters of biotin. 848 Sep 97

Analysis of the primary sequence of the cystic fibrosis transmembrane conductance regulator (CFTR) has suggested the presence of two predicted cytoplasmic regions of the protein which are thought to be nucleotide binding folds (NBF1 and NBF2). Previous studies have shown that purified recombinant NBF1 can form anion conducting channels in planar phospholipid bilayers [Arispe et al. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 1539-1543] and that the bacterial His P protein (analogous to a NBF) can be extracellularly labeled with a membrane-impermeant reagent [Baichwal et al. (1993) Proc. Natl. Acad. Sci. U.S.A. 90, 620-624]. Based on these observations, it is reasonable to hypothesize that the NBFs from the CFTR are associated with the plasma membrane and have extracellularly-accessible regions. Direct biochemical evidence for this was obtained by determining the ability of the individual NBFs, expressed in intact Hi5 cells, to be chemically modified with the membrane-impermeant reagent NHS-biotin. The results indicate that both NBF1 and NBF2, in intact cells, can be chemically modified by extracellular NHS-biotin. The negative control, the cytosolic enzyme beta-galactosidase, was not significantly labeled under these conditions, verifying the extracellular nature of the labeling reaction. When the surface-accessibility of a NBF1 construct containing the CF-causing mutation deltaF508 was analyzed, similar labeling was observed, suggesting that the mutation does not affect this aspect of the CFTR's structure. These data support the conclusion that, under certain conditions, the NBFs are capable of spanning the plasma membrane, perhaps constituting a portion of the CFTR's ion conducting channel.
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PMID:The nucleotide binding folds of the cystic fibrosis transmembrane conductance regulator are extracellularly accessible. 920 15

Adhesion of human colon carcinoma variant cell lines expressing different levels of the cell surface sialyl Lewis X (sLeX) antigen to frozen sections of mouse liver was examined. KM12-HX cells that bound the monoclonal antibody (mAb) FH6 (anti-sLeX) and thus expressed a high level of sLeX demonstrated a greater degree of adhesion to liver sections than their low-binding counterparts, KM12-LX cells. The adhesion of KM12-HX cells to liver sections was partially blocked by mAb FH6, but not by another anti-sLeX mAb, KM93. The adhesion was Ca2+ dependent but was not inhibited by anti-E-selectin. Endo-beta-galactosidase treatment significantly reduced adhesion and resulted in the loss of cell surface binding sites for mAb FH6. O-linked oligosaccharides from KM12-HX cells incubated in the presence of p-nitrophenyl-N-acetylgalactosaminide were fractionated by a combination of gel filtration, anion exchange chromatography, and normal phase high-performance liquid chromatography. The structure of a mAb FH6-reactive and endo-beta-galactosidase-sensitive glycan was estimated by matrix-assisted laser desorption ionization time-of-flight mass spectrometry in a post source decay mode and by glycosidase digestions to be NeuAc alpha2-3Gal beta1-4GlcNAc beta1-3Gal beta1-4Glc-NAc beta1-3Gal beta1-4(+/-Fuc alpha1-3)GlcNAc beta1-6(NeuAc alpha2-3Gal beta1-3)GalNAc-pNP. Mild detergent lysates of mouse liver surface-labeled with sulfo-NHS biotin were incubated with glutaraldehyde-fixed monolayers of KM12-HX cells, and bound components were isolated after EDTA treatment. A Mr 49,000 component that bound only to KM12-HX cells and not to KM12-LX cells was identified.
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PMID:Involvement of cell surface glycans in adhesion of human colon carcinoma cells to liver tissue in a frozen section assay: role of endo-beta-galactosidase-sensitive structures. 1101 56