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Biomedical subjects

J B McAlpine

Publications and source records attributed to J B McAlpine.

At least 19 recordsLinked to original sources
PubMed2001

Enterococcus faecalis multi-drug resistance transporters: application for antibiotic discovery.

Using bioinformatics approaches, 34 potential multidrug resistance (MDR) transporter sequences representing 4 different transporter families were identified in the unannotated Enterococcus faecalis database (TIGR). A functional genomics campaign generating single-gene insertional disruptions revealed several genes whose absence confers significant hypersensitivities to known antimicrobials. We constructed specific strains, disrupted in a variety of previously unpublished, putative MDR transporter genes, as tools to improve the success of whole-cell antimicrobial screening and discovery. Each of the potential transporters was inactivated at the gene level and then phenotypically characterized, both with single disruption mutants and with 2-gene mutants built upon a delta norA deleted strain background.

ATP-Binding Cassette Transporters↗
PubMed1997

Production of brominated tiacumicin derivatives.

Several novel tiacumicin derivatives containing bromine have been produced by the addition of inorganic bromine to the fermentation both of Dactylosporangium aurantiacum subsp, hamdenensis. Structures were elucidated employing mass spectrometry and NMR spectroscopy. Antibacterial activity of the bromotiacumicins is comparable to that of the parent compounds.

Actinomycetales↗
PubMed1996

A method for the selective isolation of Myxococcus directly from soil.

A new method is described for the selective isolation of species of Myxococcus directly from soil by dilution plating. The method involves suppression of competing microorganisms with antibiotics combined with air drying and wet heat treatment of soils. Fungi were eliminated by supplementing the plating medium with cycloheximide and nystatin. Non-sporulating bacteria were controlled by air drying soils and then heating aqueous soil dilutions for 10 min at 56 degrees C. The predominant sporulating bacteria in soil, Streptomyces and Bacillus, were suppressed by adding either tiacumicin B, ristocetin or vancomycin to the medium. Swarming of Myxococcus colonies was controlled with a casein digest-yeast extract plating medium (CY-C10 agar). Ultrasound treatment of soil suspensions gave the highest number of Myxococcus colonies in the soils studied, but these cultures could be recovered without ultrasound. Strains of Myxococcus fulvus, M. xanthus, M. coralloides, M. stipitatus and M. virescens were isolated from soil using this technique. Soils examined yielded one or two Myxococcus species per sample.

Aminoglycosides↗
PubMed1996

Dibefurin, a novel fungal metabolite inhibiting calcineurin phosphatase activity.

The novel calcineurin inhibitor, dibefurin, has been isolated from the fungal culture AB 1650I-759. The isolation was bioactivity-directed fractionation using an assay which measures the phosphatase activity of calcineurin. The compound was purified by countercurrent, reverse phase and gel filtration chromatographies. Several studies, including crystallographic, NMR and MS, revealed that dibefurin is a novel dimeric compound of a unique structural type.

Benzofurans↗
PubMed1996

Novel triterpene sulfates from Fusarium compactum using a rhinovirus 3C protease inhibitor screen.

Two novel triterpene sulfates have been isolated from Fusarium compactum by bioactivity-directed fractionation using an assay which measures the inhibition of proteolytic activity of rhinovirus 3C protease on a fluorogenic peptide substrate. The compounds were purified by countercurrent and reverse phase chromatographies. NMR, MS, UV and IR studies revealed two triterpene sulfates, uncommon metabolites of terrestrial fungi.

Cholestenes↗
PubMed1995

Macquarimicins, microbial metabolites from Micromonospora. I. Discovery, taxonomy, fermentation and biological properties.

A novel series of microbial metabolites were discovered in fermentation broths of two soil isolates. Both cultures were identified as strains of Micromonospora chalcea. Production of the metabolites, named macquarimicins, was monitored by an HPLC assay. A seven-day fermentation yielded 27 mg/liter of macquarimicin A. With MICs of 50 to 100 micrograms/ml, macquarimicin A has only very low activity against strains of Bacteroides and other anaerobes. Macquarimicin B has inhibitory activity against the leukemia cell line P-388.

Animals↗
PubMed1995

Macquarimicins, microbial metabolites from Micromonospora. II. Isolation and structural elucidation.

A novel series of carbocyclic compounds has been isolated from two related Micromonospora cultures. The C-19 and C-22 macquarimicins represent different end products on a similar biosynthetic scheme. 1-D and 2-D homonuclear and heteronuclear NMR experiments allowed assignment of the basic structures of the macquarimicins. An X-ray structure of macquarimicin B suggested the stereochemistry for the series which was not discernible from spectroscopic data alone.

Anti-Bacterial Agents↗
PubMed1995

Fusacandins A and B; novel antifungal antibiotics of the papulacandin class from Fusarium sambucinum. II. Isolation and structural elucidation.

Two novel antifungal compounds of the papulacandin class, named fusacandins A and B, have been isolated from Fusarium sambucinum. Each compound contains two units of galactose and one of glucose, the latter connected as a C-glycoside to an aromatic moiety. Fusacandin A is esterified at two sites with long-chain, unsaturated fatty acids and fusacandin B at only one site. The structures of the fusacandins were elucidated through analysis of mass spectral and 1-D and 2-D homonuclear and heteronuclear NMR data.

Antifungal Agents↗
PubMed1994

MLR-52, (4'-demethylamino-4',5'-dihydroxystaurosporine), a new inhibitor of protein kinase C with immunosuppressive activity.

In the course of screening with the mixed lymphocyte reaction, a new inhibitor of protein kinase C with immunosuppressive activity was isolated from the fermentation broth and mycelia of Streptomyces sp. AB 1869R-359. Although certain similarities exist, this strain is morphologically and physiologically distinct from other reported producers of staurosporine-related compounds. We have found that this strain produces relatively high levels of staurosporine and the new minor compound MLR-52, which possesses the indolo[2,3-a]carbazole chromophore of staurosporine, but differs in the substitution pattern of the sugar moiety. Their structures have been elucidated by mass and NMR spectra. MLR-52 has been shown to inhibit the enzymatic activity of protein kinase C and the murine mixed lymphocyte reaction.

Alkaloids↗
PubMed1994

Aselacins, novel compounds that inhibit binding of endothelin to its receptor. I. The producing organism, fermentation and biological activity.

A radioligand test to detect inhibitors of endothelin-1 binding to its receptors in bovine atrial and porcine cerebral membranes was used to screen fungal metabolites from stationary fermentations. Inhibitory activity, observed in culture extracts of two Acremonium species, led to the discovery of aselacins A, B and C. Aselacin A inhibits binding to both membrane fractions with IC50s of approximately 20 micrograms/ml.

Acremonium↗
PubMed1994

Aselacins, novel compounds that inhibit binding of endothelin to its receptor. II. Isolation and elucidation of structures.

Three novel compounds, named the aselacins, which inhibit the binding of endothelin to its receptor have been isolated from two related Acremonium species of fungi grown in stationary culture. These compounds are cyclic pentapeptolides with a ring formed by cyclo[Gly-D-Ser-D-Trp-beta-Ala-L-Thr] and an additional exocyclic D-Gln to which is attached a functionalized long chain fatty acid. The aselacins differ in the functionalization of this acid. The structures of the aselacins were determined by amino acid analysis, mass spectrometry and evaluation of 1-D and 2-D homonuclear and heteronuclear 1H, 13C and 15N NMR spectra in protic and aprotic solvents. The stereochemistry of the amino acids present was elucidated by chiral HPLC of hydrolyzed compound.

Acremonium↗
PubMed1994

Dorrigocins: novel antifungal antibiotics that change the morphology of ras-transformed NIH/3T3 cells to that of normal cells. II. Isolation and elucidation of structures.

Two novel antifungal antibiotics, named dorrigocin A and B have been isolated from the fermentation broth and mycelium of Streptomyces platensis subsp. rosaceus. These closely related compounds were separated from one another by countercurrent chromatography on an Ito coil planet centrifuge. The structures of the dorrigocins were determined by NMR and IR spectroscopy and mass spectrometry. Each is a putative propionate-acetate derived straight chain fatty acid terminating in cycloheximide. The dorrigocins differ from one another only in their oxidation pattern.

3T3 Cells↗
PubMed1994

Dorrigocins: novel antifungal antibiotics that change the morphology of ras-transformed NIH/3T3 cells to that of normal cells. III. Biological properties and mechanism of action.

The dorrigocins are unique glutarimide antibiotics which were found to reverse the morphology of ras-transformed NIH/3T3 cells from a transformed phenotype to a normal one. The compounds also inhibited the release of yeast mating pheromone, a-factor. The activity of these compounds was not dependent on inhibition of prenylation or protein synthesis. Dorrigocin A was instead found to inhibit the carboxyl methylation in K-ras transformed cells.

3T3 Cells↗
PubMed1993

An erythromycin analog produced by reprogramming of polyketide synthesis.

The polyketide-derived macrolactone of the antibiotic erythromycin is made through successive condensation and processing of seven three-carbon units. The fourth cycle involves complete processing of the newly formed beta-keto group (beta-keto reduction, dehydration, and enoyl reduction) to yield the methylene that will appear at C-7 of the lactone ring. Synthesis of this molecule in Saccharopolyspora erythraea is determined by the three large eryA genes, organized in six modules, each governing one condensation cycle. Two amino acid substitutions were introduced in the putative NAD(P)H binding motif in the proposed enoyl reductase domain encoded by eryAII. The metabolite produced by the resulting strain was identified as delta 6,7-anhydroerythromycin C resulting from failure of enoyl reduction during the fourth cycle of synthesis of the macrolactone. This result demonstrates the involvement of at least the enoyl reductase from the fourth module in the fourth cycle and indicates that a virtually complete macrolide can be produced through reprogramming of polyketide synthesis.

Amino Acid Sequence↗