SEARCH · Search PubMed

Results for “Biotin”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

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

At least 19 recordsLinked to original sources

PubMed1978

Uptake of extracellular biotin by Escherichia coli biotin prototrophs.

Uptake of exogenous biotin by two Escherichia coli biotin prototroph strains, K-12 and Crookes, appeared to involve incorporation at a fixed number of binding sites located at the cell membrane. Incorporation was characterized as a binding process specific for biotin, not requiring energy, and stimulated by acidic pH. Constant saturation quantities of exogenous biotin were incorporated by these cells, and the amounts, which were titrated, depended on whether the cells were resting or dividing. Resting cells incorporated exogenous biotin amounting to 2% of their total intracellular biotin content. Fifty percent of the exogenous biotin was incorporated into their free biotin fraction, and 50% was incorporated into their bound biotin fraction. On the other hand, dividing cells incorporated exogenous biotin into all of their intracellular sites, 88% going into the intracellular-bound biotin fraction, and 12% going into the free biotin fraction. Calculations suggested that each cell contained approximately 3,000 binding sites for biotin. It was postulated that biotin incorporation sites might have been components of acetyl coenzyme A carboxylase located at or near the membrane.

Avidin↗

PubMed1992

Non-isotopic receptor assay for benzodiazepines using a biotin-labeled ligand and biotin-immobilized microtiter plate.

A non-isotopic receptor assay for benzodiazepine drugs was developed using a biotin-labeled ligand, biotin-1012S. Biotinylated bovine serum albumin (biotin-BSA) was immobilized onto the wall of microtiter plate wells by simple adsorption. Avidin peroxidase conjugate could be extracted from solution owing to its strong interaction with biotin. The amount of avidin peroxidase taken up on the wall was then determined by measuring the enzyme activity. The competition between immobilized biotin on the wall and free biotin for avidin provided the basis for a solid-phase avidin-biotin binding assay. By this binding assay, not only biotin but also biotin-1012S could be measured sensitively. Because 1012S is a ligand with high affinity to benzodiazepine receptors, biotin-1012S could be utilized as a probe ligand for a non-isotopic receptor assay. Based upon the competition between biotin-1012S and various benzodiazepine drugs for the receptor binding sites, a non-isotopic receptor assay was demonstrated.

Animals↗

PubMed1975

Production of antibodies that bind biotin and inhibit biotin containing enzymes.

Methods were developed for the coupling of biotin to bovine serum albumin and bovine gamma-globulin using a water-soluble carbodimide. The use of [14-C]biotin as a tracer allowed quantitation of the incorporation of biotin into the conjugates: 2.55 mol of biotin was incorporated per mol of gamma-globulin and 7-9 mol of biotin was incorporated per mol of serum albumin in different preparations. These conjugates were highly immunogenic in the rabbit and anti-bodies reactive with the biotinyl group itself could be detected by their ability to precipitate the heterologous biotinated carrier but not the unmodified heterologous carrier. There antisera rapidly inactivated transcarboxylase and pyruvate carboxylase and this inactivation could be blocked by pretreatment of the antisera with biotin or biocytin. Using enzyme inhibition to detect free antibody, the binding constant for biotin was found to be 5.0 x 10- minus 8 M and that for biocytin 3.5 x 10- minus 8 M.

Animals↗

PubMed1992

Biotin transport in primary culture of astrocytes: effect of biotin deficiency.

The uptake of radioactive biotin has been studied in glial cell cultures from dissociated cerebral hemispheres of newborn rats. We describe saturable kinetics for the biotin uptake at biotin concentrations of less than 60 nM and linear at greater than 60 nM. The uptake appeared temperature sensitive, Na+ independent, nonsensitive to valinomycin, and not affected by metabolic inhibitors such as sodium fluoride or azide. Lipoic acid and biocytin were effective in inhibiting the biotin uptake. These findings are consistent with biotin uptake by the primary culture of astrocytes as a process of facilitated diffusion. Moreover, biotin uptake in astrocytes grown in biotin-restricted conditions was significantly higher compared with the control. This increase appeared mediated through a pronounced increase (10-fold) in the Vmax of the biotin uptake without any change in the apparent Km.

Animals↗

PubMed1978

Repression of biotin biosynthesis in Escherichia coli during growth on biotin vitamers.

A strain of Escherichia coli in which the lacZ gene was fused to the bioA promoter was constructed. Colonies of this strain formed Lac(+) colonies on low-biotin agar (1.6 to 4.1 nM) and Lac(-) colonies on high-biotin agar (41 nM). This lac-bio fusion strain was used to study the question of whether cells growing on the biotin vitamers d-biotin-d-sulfoxide (BDS) and dethiobiotin (DTB) generate enough biotin to give maximal repression of beta-galactosidase synthesis. Repression by high concentrations (400 nM) of BDS was almost maximal (about 96%), whereas DTB repression reached a saturation level of about 80% with increasing DTB concentrations. The levels of repression obtained with both vitamers were sufficient to cause the colonies to appear Lac(-). When the lac-bio fusion was transduced into lines carrying mutations (bis) that prevent reduction of BDS to biotin, the transductants were not repressed by added BDS. Repression by BDS is unlikely to result from accumulation of extracellular biotin-related substances because (i) washed bis(+) cells were not detectably derepressed when transferred into medium containing BDS and (ii) washed bis cells were not detectably repressed when transferred into medium in which bis(+) cells had grown. Lactose agar plates containing high concentrations of DTB or BDS comprise an efficient selective medium for bioB or bis mutants and were used to isolate spontaneous mutations of these genes. This method should be adaptable to the selection of mutations in any biosynthetic pathway subject to end-product repression.

Biotin↗

PubMed1977

Diester waxes from skin lipids of the feet of biotin depleted and biotin supplemented turkey poults.

The neutral lipids of the skin from the feet of turkey poults fed a biotin supplemented or a biotin deficient diet consist mainly of triacyglycerols, and of mono- and diester waxes. Diester waxes from both groups were characterized as fatty acid esters of erythro-2,3-alkanediols. A comparison between fatty acid composition of the two groups, however, revealed the following significant differences. Biotin deficient birds showed a fairly high concentration of very long chain fatty acids (C36-C40) which were completely absent in biotin supplemented birds. Further, almost one-third of the fatty acids of diester waxes in biotin deficient birds were unsaturated while those from biotin supplemented birds were predominantly (96%) saturated.

Animals↗

PubMed1992

Escherichia coli biotin holoenzyme synthetase/bio repressor crystal structure delineates the biotin- and DNA-binding domains.

The three-dimensional structure of BirA, the repressor of the Escherichia coli biotin biosynthetic operon, has been determined by x-ray crystallography and refined to a crystallographic residual of 19.0% at 2.3-A resolution. BirA is a sequence-specific DNA-binding protein that also catalyzes the formation of biotinyl-5'-adenylate from biotin and ATP and transfers the biotin moiety to other proteins. The level of biotin biosynthetic enzymes in the cell is controlled by the amount of biotinyl-5'-adenylate, which is the BirA corepressor. The structure provides an example of a transcription factor that is also an enzyme. The structure of BirA is highly asymmetric and consists of three domains. The N-terminal domain is mostly alpha-helical, contains a helix-turn-helix DNA-binding motif, and is loosely connected to the remainder of the molecule. The central domain consists of a seven-stranded mixed beta-sheet with alpha-helices covering one face. The other side of the sheet is largely solvent-exposed and contains the active site. The C-terminal domain comprises a six-stranded, antiparallel beta-sheet sandwich. The location of biotin binding is consistent with mutations that affect enzymatic activity. A nearby loop has a sequence that has been associated with phosphate binding in other proteins. It is inferred that ATP binds in this region, adjacent to the biotin. It is proposed that the binding of corepressor to monomeric BirA may promote DNA binding by facilitating the formation of a multimeric BirA-corepressor-DNA complex. The structural details of this complex remain an open question, however.

Adenosine Triphosphate↗

PubMed1978

Specific localization and quantification of biotin transport components in yeast by use of a biotin-conjugated, impermeant, electron-dense label.

Two approaches are described for the localization and quantification of biotin transport components in yeast cells. One approach is based on tracing the fate of a radioactive affinity label for the biotin transport system, [14C]biotinyl-p-nitrophenyl ester (pBNP), through various stages of subcellular fractionations. A complementary method involves the use of a biotin-derivatized, impermeant, electron-dense, affinity-cytochemical label (ferritin-biotin conjugates) for subsequent visualization by electron microscopy. Values of approximately 8,000 and 4,000 sites/cell, respectively, were achieved by the two methods. Complicating factors, future perspectives and the relevance of the two methods to the isolation of transport components are discussed.

Affinity Labels↗

PubMed1992

Biotin amplification of biotin and horseradish peroxidase signals in histochemical stains.

A procedure is described for intensifying histochemical reactions by amplification of biotinylated sites. This is achieved by deposition of biotinylated tyramine on the tissue through the enzymatic action of horseradish peroxidase (HRP). The amplified biotin sites are subsequently visualized by binding them to avidin, to which a marker is attached. This amplification greatly increases the sensitivity of staining procedures that employ HRP (and/or biotin) in tissue. For neuroanatomical pathway tracing methods, the procedure greatly increases the detectability of the injected tracer. For lectin histochemistry and immunohistochemistry, the amplification requires that the lectin or primary antibody be greatly diluted. This dilution results in less background staining and yet strong signals are produced even when very dilute reagents are used. Alternatively, the amplification permits much shorter incubations in primary antibodies when dilutions are used that would ordinarily be used with conventional bridge techniques. The procedure is also useful for amplifying very weak signals, such as those of immunoreactions in glutaraldehyde-fixed tissue. The amplification procedure, together with the availability of avidin probes labeled with fluorochromes, colloidal gold, or enzyme systems other than HRP, provides a means of greatly increasing the versatility of a variety of histochemical reactions, including those for detecting in situ hybridization probes, in addition to increasing the sensitivity of the reactions.

Animals↗

PubMed1979