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PubMed1975

Improved high-performance liquid chromatographic method for polypeptide antibiotics and its application to study the effects of treatments to reduce microbial levels in bacitracin powder.

Improvements were made in the high-performance liquid chromatographic (HPLC) method to obtain baseline separation of chromatographic peaks of structurally similar polypeptide components in bacitracin. The improved method uses a 30-cm-long stainless-stell column packed with muBondapak C18. The theoretical plates of the column are approximately 140,000 per meter for the bacitracin A peak. The resolution function between bacitracins B1 and B2 and that between bacitracins A and B2 have been improved 418 and 225%, respectively. The components of bacitracin, bacitracins A, B, C, D, E, F, and G, were fractionated by the countercurrent distribution technique. These components, together with Compound X, a compound separated on a carboxymethylcellulose column, and bacitracin F, obtained by degrading bacitracin A sample at neutral pH, were used to identify peaks in the HPLC chromatogram. Effects of processing methods used to reduce microbial contamination levels in bacitracin powders were evaluated. Heat treatment caused a significant loss of antimicrobial activity (35% reduction), bacitracins A, B1, and B2 were reduced by 37, 22, and 21%, respectively. A significant increase (2.8 times) of bacitracin F, an oxidative degradation compound, was show. Irradiation by 60Co at 1.8 Mrad caused no loss of potency nor change in any of the bacitracin components. Ethylene oxide treatment, on the other hand, caused considerable (46%) reduction of potency. Substantial reduction of areas under the peak of bacitracins A, B1, and B2 (50, 24 and 37%, respectively) were noted. The chromatograms showed numerous unresolved peaks around bacitracins A, B1 and B2,; however, no significant increase in the bacitracin F peak, nor appearance of non-UV absorbing peaks were observed. Peptide antibiotics of the polymyxin group, circulin, colistin, and polymyxin, were also analyzed using the muBondapak C18 column with a linear-gradient elution. A UV monitor was used for polymyxin. A moving-wire flame ionization detector was used to monitor circulin and colistin. A sample of polymyxin, circulin, and colistin may be analyzed in less than 20 min of chromatographic time.

Anti-Bacterial Agents↗
PubMed2003

A bacitracin-resistant Bacillus subtilis gene encodes a homologue of the membrane-spanning subunit of the Bacillus licheniformis ABC transporter.

Bacitracin is a peptide antibiotic nonribosomally produced by Bacillus licheniformis. The bcrABC genes which confer bacitracin resistance to the bacitracin producer encode ATP binding cassette (ABC) transporter proteins, which are hypothesized to pump out bacitracin from the cells. Bacillus subtilis 168, which has no bacitracin synthesizing operon, has several genes homologous to bcrABC. It was found that the disruption of ywoA, a gene homologous to bcrC, resulted in hypersensitivity to bacitracin. Resistance to other drugs such as surfactin, iturin A, vancomycin, tunicamycin, gramicidin D, valinomycin and several cationic dyes were not changed in the ywoA disruptant. Spontaneous bacitracin-resistant mutants (Bcr-1 and -2) isolated in the presence of bacitracin have a single base substitution from A to G in the ribosome binding region. Northern hybridization analysis and determination of the expression of ywoA-LacZ transcriptional fusion gene revealed that the transcription of the ywoA gene was dependent on extracytoplasmic function (ECF) sigma factors sigma(M) and sigma(X). Preincubation of wild-type cells in the presence of a low concentration of bacitracin induced increased resistance to bacitracin about two- to threefold, although the mechanism of this induction has not yet been elucidated. It has been reported that a commercially available bacitracin is a mixture of several components and also contains impurity. Bacitracin A was purified by reverse phase high-performance liquid chromatography (HPLC). Similar results were obtained with bacitracin A as those with crude bacitracin, indicating that contaminating substances were not responsible for the results obtained in this study.

ATP-Binding Cassette Transporters↗
PubMed1983

Studies on the inhibitory effect of bacitracin on 125I-labelled insulin internalization in the rat hepatocyte.

Previous studies have suggested that transglutaminase has a role in the internalization of some polypeptide hormones and is inhibited by the antibiotic, bacitracin. Bacitracin has been used in insulin-receptor studies to inhibit extracellular degradation of 125I-labelled insulin. The aim of this study was to investigate bacitracin's effect on 125I-labelled insulin-receptor interactions in isolated rat hepatocytes. 1 g/l bacitracin increased cell-associated 125I-labelled insulin insulin at 20, 30 and 37 degrees C (P less than 0.001, 0.0005 and 0.0005, respectively). At 5 and 15 degrees C (internalization does not occur), bacitracin did not affect cell-associated 125I-labelled insulin. The bacitracin effect was concentration dependent, increasing to 2 g/l. Scatchard analysis showed that bacitracin did not alter insulin receptor affinity or number. 1 g/l bacitracin abolished the effect of chloroquine. The increased cell-associated radioactivity with bacitracin was surface-bound in nature. 0.5 g/l bacitracin decreased 125I-labelled insulin degradation in hepatocyte suspensions (P less than 0.001) and in buffer previously incubated with hepatocytes (P less than 0.0005). More 125I-labelled insulin remained associated with cells during dissociation studies at 37 degrees C when the buffer contained 1 g/l bacitracin. Label that appeared in the buffer after 60 min was significantly more intact in the presence of bacitracin (P less than 0.025). These results suggest that bacitracin retards the internalization of 125I-labelled insulin in isolated rat hepatocytes.

Animals↗
PubMed1994

Structures of bacitracin A and isolated congeners: sequencing of cyclic peptides with blocked linear side chains by electrospray ionization mass spectrometry.

The bacitracin antibiotic complex consists principally of bacitracin A, a peptide antibiotic containing seven amino acid residues in a ring and five amino acid residues in a blocked side chain, together with a mixture of minor components presumably related but of unknown structures. A preparative high-performance liquid chromatographic method was developed for isolating the minor components A2, B1 and B2 which were then characterized by amino acid analysis, exact mass fast atom bombardment (FAB) mass spectrometry, FAB tandem mass spectrometry (MS/MS) and electrospray ionization (ESI) mass spectrometry. For bacitracins A (MW 1421), A2 (MW 1421), B1a (MW 1407), B1b (MW 1407), B2 (MW 1407) and F (MW 1419), the side chain sequences were determined by ESI MS/MS and ESI nozzle-skimmer collision-induced dissociation (CID) mass spectrometry and the ring sequences elucidated by ESI nozzle-skimmer CID MS/MS. Relative to bacitracin A, bacitracin A2a has the modified isoleucine residue at position 1 replaced by a modified allo-isoleucine residue, bacitracin B1a has the isoleucine residue at position 8 replaced by a valine residue, bacitracin B1b has the isoleucine residue at position 5 replaced by a valine residue and bacitracin B2 has the modified isoleucine residue at position 1 replaced by a modified valine residue. FAB tandem mass spectra were shown to be consistent with the above structural assignments for the isolated bacitracin components. Structures were also proposed for the trace bacitracin components C1 (MW 1393) and D1 (MW 1379) using ESI MS/MS data obtained from the analysis of the bacitracin complex without isolation.

Amino Acid Sequence↗
PubMed1996

Three dimensional structure of the antibiotic bacitracin A complexed to two different subtilisin proteases: novel mode of enzyme inhibition.

The three dimensional crystal structures of thermitase-bacitracin (TMTBAC), Savinase- bacitracin (SAVBAC) and Savinase-zinc/bacitracin (SAVBAC/ZN) have been determined by X-ray diffraction to 2.2 angstroms, 2.2 angstroms and 1.95 angstroms resolution, respectively. The multifunctional dodecapeptide bacitracin A secreted by Bacillus licheniformis is well known as an antibiotic against gram-positive bacteria but also as an inhibitor for different proteases. The bacteriocidal activity requires the presence of divalent metal cations such as zinc or nickel. It also could be shown that bacitracin A is bound to subtilisin in the Bacillus licheniformis. This complex is stable throughout the purification by chromatography. Therefore the subtilisin proteases thermitase and Savinase were used for cocrystallization with bacitracin A and zinc/bacitracin A. The complexes are formed from two enzyme molecules and two bacitracin A molecules. All three complexes show the same novel mode of enzyme inhibition. Each bacitracin A chain binds non-covalently to two protease molecules: to the catalytic side of one and to the substrate recognition side of the second protease molecule. In that way the two bacitracin A molecules link two subtilisin molecules together to form a dimer. Despite this common feature we found some important differences in the conformations of bacitracin A in the three complex structures which were analysed and described in detail in this paper. An examination of the solvent structure of the complexes shows water molecules in the region around the bacitracin A molecules are not conserved and play a different role in the stabilization of the bacitracin A conformation.

Anti-Bacterial Agents↗
PubMed1992

Dissociation of the antimicrobial activity of bacitracin USP from its renovascular effects.

Bacitracin is a nephrotoxic antibiotic that has recently been shown to induce contractile effects in aortas isolated from rabbits by stimulating receptors for 5-hydroxytryptamine (5-HT). The possible renovascular actions of this antibiotic were investigated. Bacitracin USP increased the vascular resistance in a concentration-dependent manner (9 to 175 micrograms/ml) in rat kidneys perfused with a constant flow of Krebs solution. This was significantly inhibited by 5-HT antagonists, but only partially at the higher bacitracin concentration. An antagonist of the chemotactic peptide fMet-Leu-Phe failed to influence the pressor effect of bacitracin in rat kidneys. Indomethacin modestly reduced the effect of all potent pressor agents in the rat organ. Bacitracin USP was separated in several fractions by using C18 reverse-phase chromatography. Two distinct fractions were vasoconstrictive when infused in rat kidneys; both fractions were 5-HT mimetics. These peaks were different from the major antibiotic peak, bacitracin A, which was identified by using analytical high-pressure liquid chromatography, mass spectrometry, and inhibition of Micrococcus luteus growth. The less polar vasoactive peak corresponded to at least two minor peptides of the bacitracin family. The most abundant of these vasoactive peptides had no direct contractile effect on an aorta isolated from a rabbit, but a preliminary metabolic study in rat kidneys suggests that it is apparently transformed into a potent 5-HT agonist that is active on the aorta preparation. Bacitracin A, the major constituent of bacitracin with antimicrobial activity, had no vasoconstrictor effect in the test systems that we used; however, we did rule out the possibility that the renovascular stimulants found in the bacitracin mixture do not derive spontaneously or by biotransformation from the antibacterial forms of bacitracin.

Animals↗
PubMed1982

Inhibition by bacitracin of rat adipocyte plasma membrane degradation of 125I-insulin is associated with an increase in plasma membrane bound insulin and a potentiation of glucose oxidation by adipocytes.

The present study demonstrated that at physiological concentrations of insulin bacitracin inhibited the degradation of specifically bound insulin by enzymes located in the rat adipocyte plasma membrane. Bacitracin increased the amount of intact insulin specifically bound to the plasma membrane and potentiated the stimulation of adipocyte glucose oxidation by submaximal concentrations of the hormone. In contrast to agents such as chloroquine, which inhibit lysosomal degradation of internalized insulin, bacitracin was shown by two approaches to inhibit a degradative process localized to the adipocyte plasma membrane. Cyanide and 2,4-dinitrophenol, agents which inhibit energy requiring endocytosis, had no effect on the bacitracin inhibition of cellular degradation of 125I-insulin. Bacitracin directly inhibited 125I-insulin degradation by isolated plasma membranes at similar concentrations and to a similar extent as found with cells. The degradative process inhibited by bacitracin accounted for the majority of cellular degradation of the hormone. The increased 125I-insulin bound to adipocytes was shown to be intact by gel chromatographic analysis and was localized to the plasma membrane by direct and indirect approaches. Bacitracin increased 125I-insulin specifically bound to isolated plasma membranes as early as 2 min. The 125I-insulin bound to adipocytes in the presence of bacitracin was completely dissociable by the addition of 8 microM unlabeled insulin whereas a significant portion of 125I-insulin bound to chloroquine-treated cells could not be dissociated. Bacitracin slowed dissociation of 125I-insulin from the cells. Bacitracin increased the 125I-insulin binding to cells in the presence and absence of cyanide and 2,4-dinitrophenol. Bacitracin potentiated the stimulation of adipocyte glucose oxidation at submaximal concentrations of insulin.

Adipose Tissue↗
PubMed1982

Bacitracin produces analgesia by increasing brain immunoreactive beta-endorphin (beta-E) content.

The effects of protease inhibitor bacitracin on brain beta-endorphin content and analgesia, were examined in vivo. Male Sprague-Dawley rats were injected with bacitracin intracerebroventricularly and sacrificed by microwave irradiation 15 and 30 min after injection. Brain beta-endorphin levels were 27% higher in bacitracin treated rats than in controls. A second group of bacitracin injected rats was subjected to continuous intermittent 55 degrees C hot plate exposure. Bacitracin-injected rats exhibited total analgesia 15 min after bacitracin injection. At 30 min, this analgesic effect subsided. Control rats exhibited no analgesia. Bacitracin induced analgesia was naloxone reversible at a low dose of naloxone (1 mg/kg). At a higher dose of naloxone (10mg/kg), bacitracin induced analgesia was only partially antagonized. These results suggest that bacitracin induced analgesia might be due to the elevated levels of brain beta-endorphin caused by a decrease in its breakdown by bacitracin.

Analgesics↗
PubMed2000

Proton NMR studies of Co(II) complexes of the peptide antibiotic bacitracin and analogues: insight into structure-activity relationship.

Bacitracin is a widely used metal-dependent peptide antibiotic produced by Bacillus subtilis and Bacillus licheniformis with a potent bactericidal activity directed primarily against Gram-positive organisms. This antibiotic requires a divalent metal ion such as Zn(II) for its biological activity, and has been reported to bind several other transition metal ions, including Co(II), Ni(II), and Cu(II). Despite the wide use of bacitracin, a structure-activity relationship for this drug has not been established, and the structure of its metal complexes has not been fully determined. We report here one- and two-dimensional nuclear magnetic resonance (NMR) studies of the structure of the metal complexes of several bacitracin analogues by the use of paramagnetic Co(II) as a probe. The Co(II) complex of this antibiotic exhibits many well-resolved isotropically shifted (1)H NMR signals in a large spectral window ( approximately 200 ppm) due to protons near the metal, resulting from both contact and dipolar shift mechanisms. The assignment of the isotropically shifted (1)H NMR features concludes that bacitracin A(1), the most potent component of the bacitracin mixture, binds to Co(II) via the His-10 imidazole ring N(epsilon), the thiazoline nitrogen, and the monodentate Glu-4 carboxylate to form a labile complex in aqueous solutions. The free amine of Ile-1 does not bind Co(II). Several different analogues of bacitracin have also been isolated or prepared, and the studies of their Co(II) binding properties further indicate that the antimicrobial activity of these derivatives correlates directly to their metal binding mode. For example, the isotropically shifted (1)H NMR spectral features of the high-potent bacitracin analogues, including bacitracins A(1), B(1), and B(2), are virtually identical. However, Glu-4 and/or the thiazoline ring does not bind Co(II) in the bacitracin analogues with low antibiotic activities, including bacitracins A(2) and F.

Anti-Bacterial Agents↗
PubMed2002

Genes involved in bacitracin resistance in Streptococcus mutans.

Streptococcus mutans is resistant to bacitracin, which is a peptide antibiotic produced by certain species of Bacillus. The purpose of this study was to clarify the bacitracin resistance mechanism of S. mutans. We cloned and sequenced two S. mutans loci that are involved in bacitracin resistance. The rgp locus, which is located downstream from rmlD, contains six rgp genes (rgpA to rgpF) that are involved in rhamnose-glucose polysaccharide (RGP) synthesis in S. mutans. The inactivation of RGP synthesis in S. mutans resulted in an approximately fivefold-higher sensitivity to bacitracin relative to that observed for the wild-type strain Xc. The second bacitracin resistance locus comprised four mbr genes (mbrA, mbrB, mbrC, and mbrD) and was located immediately downstream from gtfC, which encodes the water-insoluble glucan-synthesizing enzyme. Although the bacitracin sensitivities of mutants that had defects in flanking genes were similar to that of the parental strain Xc, mutants that were defective in mbrA, mbrB, mbrC, or mbrD were about 100 to 120 times more sensitive to bacitracin than strain Xc. In addition, a mutant that was defective in all of the mbrABCD genes and rgpA was more sensitive to bacitracin than either the RGP or Mbr mutants. We conclude that RGP synthesis is related to bacitracin resistance in S. mutans and that the mbr genes modulate resistance to bacitracin via an unknown mechanism that is independent of RGP synthesis.

Anti-Bacterial Agents↗
PubMed2004

Acquired bacitracin resistance in Enterococcus faecalis is mediated by an ABC transporter and a novel regulatory protein, BcrR.

Bacitracin resistance (bacitracin MIC, >/=256 microg ml(-1)) has been reported in Enterococcus faecalis, and in the present study we report on the genetic basis for this resistance. Mutagenesis was carried out with transposon Tn917 to select for E. faecalis mutants with decreased resistance to bacitracin. Two bacitracin-sensitive mutants (MICs, 32 microg ml(-1)) were obtained and Tn917 insertions were mapped to genes designated bcrA and bcrB. The amino acid sequences of BcrA (ATP-binding domain) and BrcB (membrane-spanning domain) are predicted to constitute a homodimeric ATP-binding cassette (ABC) transporter, the function of which is essential for bacitracin resistance in E. faecalis. The bcrA and bcrB genes were organized in an operon with a third gene, bcrD, that had homology to undecaprenol kinases. Northern analysis demonstrated that bcrA, bcrB, and bcrD were transcribed as a polycistronic message that was induced by increasing concentrations of bacitracin but not by other cell wall-active antimicrobials (e.g., vancomycin). Upstream of the bcrABD operon was a putative regulatory gene, bcrR. The bcrR gene was expressed constitutively, and deletion of bcrR resulted in a bacitracin-sensitive phenotype. No bcrABD expression was observed in a bcrR mutant, suggesting that BcrR is an activator of genes essential for bacitracin resistance (i.e., bcrABD). The bacitracin resistance genes were found to be located on a plasmid that transferred at a high frequency to E. faecalis strain JH2-2. This report represents the first description of genes that are essential for acquired bacitracin resistance in E. faecalis.

ATP-Binding Cassette Transporters↗
PubMed1994

The sensitivity of axenic 200:NIH Entamoeba histolytica to bacitracin and its zinc salt.

This study extends the previous knowledge of the action of bacitracin zinc against xenic cultures of Entamoeba histolytica. Results presented here, using axenic E. histolytica, confirm the enhanced activity of bacitracin zinc as compared to native bacitracin and demonstrate that this enhancement is due to a direct effect upon the trophozoite. In the presence of zinc, amoebastatic concentrations of bacitracin became amoebacidal. The expression of the amoebacidal characteristics of 5 g/l bacitracin zinc following 24-35 h incubation coincided with the return of cell division by amoeba exposed to the same concentration of native bacitracin. The activity of both bacitracin and bacitracin zinc on trophozoites was unaffected by autoclaving, indicating a mode of action different from that exerted on Staphylococcus aureus. In contrast to previous clinical observations, no synergism could be detected between bacitracin and neomycin.

Animals↗
PubMed2003

Cell wall stress responses in Bacillus subtilis: the regulatory network of the bacitracin stimulon.

In response to sublethal concentrations of antibiotics, bacteria often induce an adaptive response that can contribute to antibiotic resistance. We report the response of Bacillus subtilis to bacitracin, an inhibitor of cell wall biosynthesis found in its natural environment. Analysis of the global transcriptional profile of bacitracin-treated cells reveals a response orchestrated by two alternative sigma factors (sigmaB and sigmaM) and three two-component systems (YvqEC, YvcPQ and BceRS). All three two-component systems are located next to target genes that are strongly induced by bacitracin, and the corresponding histidine kinases share an unusual topology: they lack about 100 amino acids in their extracellular sensing domain, which is almost entirely buried in the cytoplasmic membrane. Sequence analysis indicates that this novel N-terminal sensing domain is a characteristic feature of a subfamily of histidine kinases, found almost entirely in Gram-positive bacteria and frequently linked to ABC transporters. A systematic mutational analysis of bacitracin-induced genes led to the identification of a new bacitracin-resistance determinant, bceAB, encoding a putative ABC transporter. The bcrC bacitracin resistance gene, which is under the dual control of sigmaX and sigmaM, was also induced by bacitracin. By comparing the bacitracin and the vancomycin stimulons, we can differentiate between loci induced specifically by bacitracin and those that are induced by multiple cell wall-active antibiotics.

Anti-Bacterial Agents↗
PubMed1986

Cell type-specific variability of bacitracin's effects on insulin binding and intracellular accumulation.

Bacitracin is known to inhibit proteolytic degradation of insulin and several other peptide hormones. Previous work with isolated rat adipocytes showed that bacitracin blocked insulin degradation by the plasma membrane and, even in the absence of detectable insulin degradation, bacitracin increased insulin binding by decreasing the rate of insulin dissociation. The present study examined the effects of bacitracin on insulin binding and degradation and on levels of intracellular insulin in a variety of cell types. Bacitracin inhibited insulin degradation in all cell types. Maximal inhibition varied from 70% (H4IIEC3 hepatoma cells) to 95% (rat adipocytes); concentrations giving half-maximal inhibition varied from 25 microM (3T3-A31 fibroblasts) to 250 microM (H4IIEC3). Dose-response curves showed three distinctive effects on insulin binding: dose-dependent stimulation (rat adipocytes), a biphasic curve with slight stimulation at low doses and inhibition at concentrations greater than 50 microM (human fibroblasts, H4IIEC3, and 3T3-L1 adipocytes), or dose-dependent inhibition of binding (3T3-L1 preadipocytes and 3T3-A31 fibroblasts). The intracellular accumulation of insulin rat adipocytes was not affected by bacitracin but was decreased in all other cell types. These data illustrated type-specific variability in the effects of bacitracin on insulin processing resulting from cellular heterogeneity either in processing insulin or in response to bacitracin, or both, and suggest that insulin binding studies performed in the presence of bacitracin can be biased.

Adipose Tissue↗
PubMed1987

Bacitracin: a unique topical antibiotic sensitizer.

Topical bacitracin appears to be unique for the following reasons: (1) It is becoming a frequent sensitizer, particularly when used after surgery. (2) It may cause not only a delayed, eczematous contact dermatitis but an immediate urticarial reaction and, rarely, anaphylactic shock. (3) Positive patch test reactions to bacitracin often do not appear at the usual 48-hour test reading but may be positive when read at 96 hours. (4) Zinc bacitracin and "plain" bacitracin are two forms of topical bacitracin available, with possibly different degrees of sensitizing potential. (5) Bacitracin injected intradermally has been reported to be a histamine-releasing agent. (6) Bacitracin often coreacts but does not cross-react with neomycin. In this presentation we document the clinical and patch test findings of nine patients seen in the past year with allergic contact dermatitis to bacitracin ointment.

Administration, Topical↗
PubMed2005

Intraoperative anaphylaxis to bacitracin during pacemaker change and laser lead extraction.

BACKGROUND: Bacitracin is widely used in operating rooms to soak implants, irrigate compound fractures, and apply to surgical incisions. However, bacitracin is a known sensitizer and causes not only allergic contact dermatitis but also anaphylaxis. OBJECTIVE: To describe a 72-year-old woman with anaphylaxis after irrigation and packing of an infected pacemaker pocket with a bacitracin solution. METHODS: Skin prick testing to bacitracin and latex; serum tryptase, serum histamine, serum IgE to latex, and serial cardiac enzyme measurements; blood cultures, transthoracic echocardiograms, and venograms were performed to characterize the reaction. RESULTS: Six hours after the anaphylactic event, the patient had an elevated serum tryptase level of 49 ng/mL (reference range, 2-10 ng/mL), which normalized the next morning. She had immediate-type skin prick test reactions to full-strength bacitracin ointment (500 U/g) and bacitracin solution (150 U/mL). Serum IgE level to latex was undetectable, and results of skin testing to latex were negative. CONCLUSIONS: To our knowledge, this is the first case report of anaphylaxis to bacitracin during pacemaker surgery. This case illustrates that intraoperative anaphylaxis to bacitracin can be life-threatening.

Aged↗
PubMed1983

Metabolic effects of bacitracin in isolated rat hepatocytes.

Bacitracin is a proteolytic inhibitor which interacts with the intracellular processing of insulin. Its effects on pyruvate, fatty acid and amino acid metabolism were examined in rat hepatocyte suspensions. Bacitracin (0.25-1.0 mM) increased the oxidation of [1-14C]pyruvate by 50-70% and presumably therefore increased the flux through pyruvate dehydrogenase. This was found both in the presence of extracellular Ca2+ and in its absence, but not in the presence of 2 mM-2-chloropropionate, which inhibits pyruvate dehydrogenase kinase. Insulin did not further stimulate [1-14C]pyruvate oxidation in the presence of 1 mM-bacitracin. Bacitracin decreased 14CO2 formation from [2-14C]pyruvate (20-40%) and [U-14C]palmitate (30-70%), suggesting a decreased flux through the tricarboxylic acid cycle. Fatty acid oxidation before acetyl-CoA formation was also decreased. Bacitracin decreased the incorporation of label from [3H]leucine into protein in the absence of insulin, but not in its presence. Bacitracin is commonly used in studies on insulin action. Our results suggest that in such studies the effects noted may be related not only to an interaction of bacitracin with the intracellular processing of insulin but also to direct metabolic effects of bacitracin independent of insulin.

Adenine Nucleotides↗
PubMedDate not supplied

[Physico-chemical properties of the complexes of bacitracin with DNA and its effect on the process of transcription in vitro].

The aim of the present paper was to study the action of one of the peptide antibiotics, bacitracin, as the regulator of gene activity at the transcription level. Therefore the commercial bacitracin has been fractionated into two main parts by paper chromotography. These two fractions have been identified as bacitracin A (biologically active) and bacitracin F (biologically inactive). The binding of both fractions to DNA has been studied. It has been shown that bacitracin A stabilizes DNA to a lesser degree than bacitracin F does. DNA-bacitracin complexes are formed in the major groove of the DNA helix by hydrogen bonds. The analysis of the the obtained experimental data allows us to suppose that bacitracin binding to DNA has a very specific character and that this antibiotic may act as the regulator of gene activity.

Bacitracin↗