Biomedical subjects

Angela Basilio

Publications and source records attributed to Angela Basilio.

7 recordsLinked to original sources

PubMed2006

Discovery of lucensimycins A and B from Streptomyces lucensis MA7349 using an antisense strategy.

Inhibition of protein synthesis is one of the validated and highly successful targets for inhibition of bacterial growth; this mechanism is a target of a large number of clinical drugs. Ribosomal protein S4, a primary protein, is a potential target for the discovery of antibacterial agents. We describe, using an antisense-sensitized rpsD Streptomyces aureus strain, the discovery and activity of lucensimycins A and B. [structure: see text].

Anti-Bacterial Agents↗

PubMed2006

Isolation, structure, and absolute stereochemistry of platensimycin, a broad spectrum antibiotic discovered using an antisense differential sensitivity strategy.

Fatty acids are essential for survival of bacteria and are synthesized by a series of enzymes including the elongation enzymes, beta-ketoacyl acyl carrier protein synthase I/II (FabF/B). Inhibition of fatty acid synthesis is one of the new targets for the discovery and development of antibacterial agents. Platensimycin (1a) is a novel broad spectrum Gram-positive antibiotic produced by Streptomyces platensis. It was discovered by target-based whole-cell screening strategy using antisense differential sensitivity assay. It inhibits bacterial growth by selectively inhibiting condensing enzyme FabF of the fatty acid synthesis pathway and was isolated by a two-step process, a capture step followed by reversed-phase HPLC. The structure was elucidated by 2D NMR methods and confirmed by X-ray crystallographic analysis of a bromo derivative. It was determined that potential reactivity of the enone moiety does not play a key role in the biological activity of platensimycin. However, cyclohexenone ring conformation renders for the stronger binding interaction with the enzyme. The isolation, structure elucidation, derivatization, and biological activity of 6,7-dihydroplatensimycin are described.

Adamantane↗

PubMed2006

Platensimycin is a selective FabF inhibitor with potent antibiotic properties.

Bacterial infection remains a serious threat to human lives because of emerging resistance to existing antibiotics. Although the scientific community has avidly pursued the discovery of new antibiotics that interact with new targets, these efforts have met with limited success since the early 1960s. Here we report the discovery of platensimycin, a previously unknown class of antibiotics produced by Streptomyces platensis. Platensimycin demonstrates strong, broad-spectrum Gram-positive antibacterial activity by selectively inhibiting cellular lipid biosynthesis. We show that this anti-bacterial effect is exerted through the selective targeting of beta-ketoacyl-(acyl-carrier-protein (ACP)) synthase I/II (FabF/B) in the synthetic pathway of fatty acids. Direct binding assays show that platensimycin interacts specifically with the acyl-enzyme intermediate of the target protein, and X-ray crystallographic studies reveal that a specific conformational change that occurs on acylation must take place before the inhibitor can bind. Treatment with platensimycin eradicates Staphylococcus aureus infection in mice. Because of its unique mode of action, platensimycin shows no cross-resistance to other key antibiotic-resistant strains tested, including methicillin-resistant S. aureus, vancomycin-intermediate S. aureus and vancomycin-resistant enterococci. Platensimycin is the most potent inhibitor reported for the FabF/B condensing enzymes, and is the only inhibitor of these targets that shows broad-spectrum activity, in vivo efficacy and no observed toxicity.

3-Oxoacyl-(Acyl-Carrier-Protein) Synthase↗

PubMed2006

Discovery of bacterial fatty acid synthase inhibitors from a Phoma species as antimicrobial agents using a new antisense-based strategy.

Fatty acids are essential for bacterial growth and viability, with the type II fatty acid synthesis (FAS II) pathway being a potential antibacterial target. A new, selective, and highly sensitive whole cell-based antisense strategy has been designed to screen for natural product inhibitors of FabH/F of the FAS II pathway using a high-throughput two-plate agar-based differential sensitivity assay (FabF(2)p). An antisense assay along with the FASII enzyme prepared from Staphylococcus aureus was used for bioactivity-guided fractionation, leading to the isolation of phomallenic acids A-C (1-3) from a leaf litter fungus identified as Phoma sp. Compounds 1-3 exhibited minimum detection concentrations (MDC) of 0.63, 0.31, and 0.15 microg/mL in the FabF(2P) assay, IC(50) values of 22, 3.4, and 0.77 microg/mL in the FASII enzyme assay, and minimum inhibitory concentrations (MIC) of 250, 7.8, and 3.9 microg/mL, respectively, against wild-type S. aureus. Phomallenic acid C (3), the analogue with the longest chain, exhibited the best overall activity within the phomallenic acids obtained and was superior to cerulenin and thiolactomycin, the two most studied and commonly used FabF inhibitors.

Acetyltransferases↗

PubMed2006

Discovery of FabH/FabF inhibitors from natural products.

Condensing enzymes are essential in type II fatty acid synthesis and are promising targets for antibacterial drug discovery. Recently, a new approach using a xylose-inducible plasmid to express antisense RNA in Staphylococcus aureus has been described; however, the actual mechanism was not delineated. In this paper, the mechanism of decreased target protein production by expression of antisense RNA was investigated using Northern blotting. This revealed that the antisense RNA acts posttranscriptionally by targeting mRNA, leading to 5' mRNA degradation. Using this technology, a two-plate assay was developed in order to identify FabF/FabH target-specific cell-permeable inhibitors by screening of natural product extracts. Over 250,000 natural product fermentation broths were screened and then confirmed in biochemical assays, yielding a hit rate of 0.1%. All known natural product FabH and FabF inhibitors, including cerulenin, thiolactomycin, thiotetromycin, and Tü3010, were discovered using this whole-cell mechanism-based screening approach. Phomallenic acids, which are new inhibitors of FabF, were also discovered. These new inhibitors exhibited target selectivity in the gel elongation assay and in the whole-cell-based two-plate assay. Phomallenic acid C showed good antibacterial activity, about 20-fold better than that of thiolactomycin and cerulenin, against S. aureus. It exhibited a spectrum of antibacterial activity against clinically important pathogens including methicillin-resistant Staphylococcus aureus, Bacillus subtilis, and Haemophilus influenzae.

3-Oxoacyl-(Acyl-Carrier-Protein) Synthase↗

PubMed2005

Screening of antimicrobial activities in Trichoderma isolates representing three trichoderma sections.

Methanol extracts from 24 Trichoderma isolates, selected as biocontrol agents and representating different species and genotypes from three of the four taxonomic sections of this genus (T. sect. Trichoderma, T. sect. Pachybasium and T. sect. Longibrachiatum) were screened for antibacterial, anti-yeast and antifungal activities against a panel of seven bacteria, seven yeasts and six filamentous fungi previously used in similar studies. Two different growth media were tested (potato dextrose broth and CYS80), and all isolates included in the antimicrobial tests showed at least one inhibitory activity against one of the target microorganisms in one of the two culture media. No statistically significant differences were detected in the number of active strains between the two culture media, but the highest number of inhibitory strains against bacteria and fungi were found in strains from Trichoderma sect. Pachybasium, whereas strains from T. sect. Longibrachiatum showed the highest anti-yeast values. In all cases, a correlation was found between the strains that were active against yeasts and fungi. However, some degree of variability was detected for strains within the same taxonomic section. In general terms, strains from T. asperellum (mainly in CYS80 medium), and T. longibrachiatum gave the best non-enzymatic antimicrobial profiles.

Anti-Bacterial Agents↗

PubMedDate not supplied

Studies on Morinia: recognition of Morinia longiappendiculata sp. nov. as a new endophytic fungus, and a new circumscription of Morinia pestalozzioides.

A new coelomycete, Morinia longiappendiculata sp. nov., isolated from living stems of four plant species in central Spain, is described. The distinctive morphological characteristics of this fungus are the production of conidia with long basal and apical appendages on filiform conidiogenous cells that contrasts with the short-appendaged conidia and cylindrical conidiogenic cells of the type species, M. pestalozzioides. Comparative sequence analysis of the ITS rDNA region and fragments of the translation elongation factor 1alpha, actin and chitin synthase 1 genes and the study of the HPLC profiles of the M. longiappendiculata and M. pestalozzioides isolates supported the recognition of the new species. Comparison of the ITS rDNA sequences of the Morinia isolates with GenBank sequences indicated that the genus belongs to the Amphisphaeriaceae with the highest similarity to Bartalinia and Truncatella. Bresadola's original definition of M. pestalozzioides is updated by adding information on conidiogenesis and molecular data. A lectotype and epitype are designated for the species. A study of bioactive metabolites revealed that M. pestalozzioides cultures produced moriniafungin, a novel sordarin analog with potent antifungal activity.

Actins↗