RÉSUMÉ
Lipoic acid is an eight-carbon sulfur-containing biomolecule that functions primarily as a cofactor in several multienzyme complexes. It is biosynthesized as an attachment to a specific lysyl residue on one of the subunits of these multienzyme complexes. In Escherichia coli and many other organisms, this biosynthetic pathway involves two dedicated proteins: octanoyltransferase (LipB) and lipoyl synthase (LipA). LipB transfers an n-octanoyl chain from the octanoyl-acyl carrier protein to the target lysyl residue, and then, LipA attaches two sulfur atoms (one at C6 and one at C8) to give the final lipoyl cofactor. All classical lipoyl synthases (LSs) are radical S-adenosylmethionine (SAM) enzymes, which use an [Fe4S4] cluster to reductively cleave SAM to generate a 5'-deoxyadenosyl 5'-radical. Classical LSs also contain a second [Fe4S4] cluster that serves as the source of both appended sulfur atoms. Recently, a novel pathway for generating the lipoyl cofactor was reported. This pathway replaces the canonical LS with two proteins, LipS1 and LipS2, which act together to catalyze formation of the lipoyl cofactor. In this work, we further characterize LipS1 and LipS2 biochemically and spectroscopically. Although LipS1 and LipS2 were previously annotated as biotin synthases, we show that both proteins, unlike E. coli biotin synthase, contain two [Fe4S4] clusters. We identify the cluster ligands to both iron-sulfur clusters in both proteins and show that LipS2 acts only on an octanoyl-containing substrate, while LipS1 acts only on an 8-mercaptooctanoyl-containing substrate. Therefore, similarly to E. coli biotin synthase and in contrast to E. coli LipA, sulfur attachment takes place initially at the terminal carbon (C8) and then at the C6 methylene carbon.
RÉSUMÉ
Targeting Streptococcus mutans is the primary focus in reducing dental caries, one of the most common maladies in the world. Previously, our groups discovered a potent bactericidal biaryl compound that was inspired by the natural product honokiol. Herein, a structure activity relationship (SAR) study to ascertain structural motifs key to inhibition is outlined. Furthermore, mechanism studies show that bacterial membrane disruption is central to the bacterial growth inhibition. During this process, it was discovered that analog C2 demonstrated a 4-fold better therapeutic index compared to the commercially available antimicrobial cetylpyridinium chloride (CPC) making it a viable alternative for oral care.
Sujet(s)
Antibactériens/pharmacologie , Biofilms/effets des médicaments et des substances chimiques , Dérivés du biphényle/pharmacologie , Cétylpyridinium/pharmacologie , Lignanes/pharmacologie , Streptococcus mutans/effets des médicaments et des substances chimiques , Antibactériens/isolement et purification , Membrane bactérienne externe/effets des médicaments et des substances chimiques , Dérivés du biphényle/composition chimique , Lignanes/composition chimique , Tests de sensibilité microbienne , Microbiote/effets des médicaments et des substances chimiques , Phénols/isolement et purification , Phénols/pharmacologie , Streptococcus mutans/croissance et développementRÉSUMÉ
The prevalence of biofilm diseases, and dental caries in particular, have encouraged extensive research on S. mutans biofilms, including methods of preventing its formation. Numerous small molecules with specific anti-biofilm activity against this pathogen have been isolated and synthesized. Generally, these molecules can be characterized into three categories: sucrose-dependent anti-adhesion, sucrose-independent anti-adhesion and cellular signaling interference. This review aims to provide an overview of the current small molecule strategies used for targeting S. mutans biofilms, and a perspective of the future for the field.
RÉSUMÉ
Understanding the broader biological impact of carolacton, a macrolactone natural product, has been ongoing for the past decade. Multiple studies have shown connections to regulatory systems, acid tolerance mechanisms, biofilm formation, and recently folate dehydrogenase (FolD). Progress elucidating the cause of biofilm-specific activity in Streptococcus mutans has been limited due to low-throughput analyses of carolacton-treated cells. We disclose the discovery of a simplified carolacton-inspired analog that demonstrates inhibitory activity against S. mutans biofilm cells. This discovery permitted a proof of concept chemical genetic screen of S. mutans mutants identifying the carbon catabolite protein A signaling pathway as a putative target.
Sujet(s)
Biofilms/effets des médicaments et des substances chimiques , Macrolides/composition chimique , Macrolides/pharmacologie , Streptococcus mutans/effets des médicaments et des substances chimiques , Streptococcus mutans/génétique , Biofilms/croissance et développement , Produits biologiques/composition chimique , Produits biologiques/pharmacologie , Tests de sensibilité microbienne , Mutation , Étude de validation de principe , Transduction du signal , Protéine A staphylococcique/métabolisme , Streptococcus mutans/composition chimiqueRÉSUMÉ
Natural products represent a rich source of antibiotics that address versatile cellular targets. The deconvolution of their targets via chemical proteomics is often challenged by the introduction of large photocrosslinkers. Here we applied elegaphenone, a largely uncharacterized natural product antibiotic bearing a native benzophenone core scaffold, for affinity-based protein profiling (AfBPP) in Gram-positive and Gram-negative bacteria. This study utilizes the alkynylated natural product scaffold as a probe to uncover intriguing biological interactions with the transcriptional regulator AlgP. Furthermore, proteome profiling of a Pseudomonas aeruginosa AlgP transposon mutant provided unique insights into the mode of action. Elegaphenone enhanced the elimination of intracellular P.â aeruginosa in macrophages exposed to sub-inhibitory concentrations of the fluoroquinolone antibiotic norfloxacin.
Sujet(s)
Antibactériens/pharmacologie , Benzophénones/pharmacologie , Produits biologiques/pharmacologie , Pseudomonas aeruginosa/effets des médicaments et des substances chimiques , Antibactériens/synthèse chimique , Antibactériens/composition chimique , Benzophénones/synthèse chimique , Benzophénones/composition chimique , Produits biologiques/synthèse chimique , Produits biologiques/composition chimique , Cellules cultivées , Relation dose-effet des médicaments , Humains , Macrophages/effets des médicaments et des substances chimiques , Macrophages/microbiologie , Tests de sensibilité microbienne , Structure moléculaire , Norfloxacine/antagonistes et inhibiteurs , Norfloxacine/composition chimique , Norfloxacine/pharmacologie , Pseudomonas aeruginosa/cytologie , Relation structure-activitéRÉSUMÉ
The oral microbiome is a complex ecological niche where both commensal and pathogenic bacteria coexist. Previous reports have cited that the plant isolate honokiol is a potent inhibitor of S. mutans biofilms. Herein we report a cross-coupling method that provides access to a concise library of honokiol-inspired analogs. Through this work we determined that the inhibitory activity of honokiol is highly dependent on the growth conditions. Further, we identify a series of analogs that display significant potency against oral bacteria leading to the discovery of a potent antimicrobial.
Sujet(s)
Antibactériens/composition chimique , Antibactériens/pharmacologie , Bactéries/effets des médicaments et des substances chimiques , Infections bactériennes/microbiologie , Dérivés du biphényle/composition chimique , Dérivés du biphényle/pharmacologie , Lignanes/composition chimique , Lignanes/pharmacologie , Stomatite/microbiologie , Antibactériens/usage thérapeutique , Infections bactériennes/traitement médicamenteux , Biofilms/effets des médicaments et des substances chimiques , Dérivés du biphényle/usage thérapeutique , Humains , Lignanes/usage thérapeutique , Tests de sensibilité microbienne , Stomatite/traitement médicamenteuxRÉSUMÉ
The oral microbiome is a dynamic environment inhabited by both commensals and pathogens. Among these is Streptococcus mutans, the causative agent of dental caries, the most prevalent childhood disease. Carolacton has remarkably specific activity against S. mutans, causing acid-mediated cell death during biofilm formation; however, its complex structure limits its utility. Herein, we report the diverted total synthesis and biological evaluation of a rationally designed library of simplified analogs that unveiled three unique biofilm phenotypes further validating the role of natural product synthesis in the discovery of new biological phenomena.