Chemoproteomics Reveals Disruption of Metal Homeostasis and Metalloproteins by the Antibiotic Holomycin.

The natural product holomycin contains a unique cyclic ene-disulfide and exhibits broad-spectrum antimicrobial activities. Reduced holomycin chelates metal ions with a high affinity and disrupts metal homeostasis in the cell. To identify cellular metalloproteins inhibited by holomycin, reactive-cysteine profiling was performed using isotopic tandem orthogonal proteolysis-activity-based protein profiling (isoTOP-ABPP).

Inhibition of Isoleucyl-tRNA Synthetase by the Hybrid Antibiotic Thiomarinol.

Hybrid antibiotics are an emerging antimicrobial strategy to overcome antibiotic resistance. The natural product thiomarinol A is a hybrid of two antibiotics: holothin, a dithiolopyrrolone (DTP), and marinolic acid, a close analogue of the drug mupirocin that is used to treat methicillin-resistant (MRSA). DTPs disrupt metal homeostasis by chelating metal ions in cells, whereas mupirocin targets the essential enzyme isoleucyl-tRNA synthetase (IleRS).

The Antibiotic Resistome: A Guide for the Discovery of Natural Products as Antimicrobial Agents.

The use of life-saving antibiotics has long been plagued by the ability of pathogenic bacteria to acquire and develop an array of antibiotic resistance mechanisms. The sum of these resistance mechanisms, the antibiotic resistome, is a formidable threat to antibiotic discovery, development, and use. The study and understanding of the molecular mechanisms in the resistome provide the basis for traditional approaches to combat resistance, including semisynthetic modification of naturally occurring antibiotic scaffolds, the development of adjuvant therapies that overcome resistance mechanisms, and the total synthesis of new antibiotics and their analogues.

Targeted Rediscovery and Biosynthesis of the Farnesyl-Transferase Inhibitor Pepticinnamin E.

The natural product pepticinnamin E potently inhibits protein farnesyl transferases and has potential applications in treating cancer and malaria. Pepticinnamin E contains a rare N-terminal cinnamoyl moiety as well as several nonproteinogenic amino acids, including the unusual 2-chloro-3-hydroxy-4-methoxy-N-methyl-L-phenylalanine. The biosynthesis of pepticinnamin E has remained uncharacterized because its original producing strain is no longer available.

Reducing Holomycin Thiosulfonate to its Disulfide with Thiols.

The dithiolopyrrolone (DTP) natural products contain a unique ene-disulfide that is essential for their antimicrobial and anticancer activities. The ene-disulfide in some DTPs is oxidized to a cyclic thiosulfonate, but it is unknown how the DTP thiosulfonates react with biomolecules. We studied the reactivity of the thiosulfonate derivative of the DTP holomycin, oxo-holomycin, and discovered a unique redox reaction: Oxo-holomycin is reduced to its parent disulfide, while oxidizing small molecule and protein thiols to disulfides.

Role for dithiolopyrrolones in disrupting bacterial metal homeostasis.

Natural products harbor unique and complex structures that provide valuable antibiotic scaffolds. With an increase in antibiotic resistance, natural products once again hold promise for new antimicrobial therapies, especially those with unique scaffolds that have been overlooked due to a lack of understanding of how they function. Dithiolopyrrolones (DTPs) are an underexplored class of disulfide-containing natural products, which exhibit potent antimicrobial activities against multidrug-resistant pathogens.

Direct Capture Technologies for Genomics-Guided Discovery of Natural Products.

Microbes are important producers of natural products, which have played key roles in understanding biology and treating disease. However, the full potential of microbes to produce natural products has yet to be realized; the overwhelming majority of natural product gene clusters encoded in microbial genomes remain "cryptic", and have not been expressed or characterized. In contrast to the fast-growing number of genomic sequences and bioinformatic tools, methods to connect these genes to natural product molecules are still limited, creating a bottleneck in genome-mining efforts to discover novel natural products.

Chemoenzymatic synthesis of thiazolyl peptide natural products featuring an enzyme-catalyzed formal [4 + 2] cycloaddition.

Thiocillins from Bacillus cereus ATCC 14579 are members of the well-known thiazolyl peptide class of natural product antibiotics, the biosynthesis of which has recently been shown to proceed via post-translational modification of ribosomally encoded precursor peptides. It has long been hypothesized that the final step of thiazolyl peptide biosynthesis involves a formal [4 + 2] cycloaddition between two dehydroalanines, a unique transformation that had eluded enzymatic characterization. Here we demonstrate that TclM, a single enzyme from the thiocillin biosynthetic pathway, catalyzes this transformation.