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Identification of KasA as the cellular target of an anti-tubercular scaffold.

ABSTRACT: Phenotypic screens for bactericidal compounds are starting to yield promising hits against tuberculosis. In this regard, whole-genome sequencing of spontaneous resistant mutants generated against an indazole sulfonamide (GSK3011724A) identifies several specific single-nucleotide polymorphisms in the essential Mycobacterium tuberculosis ?-ketoacyl synthase (kas) A gene. Here, this genomic-based target assignment is confirmed by biochemical assays, chemical proteomics and structural resolution of a KasA-GSK3011724A complex by X-ray crystallography. Finally, M. tuberculosis GSK3011724A-resistant mutants increase the in vitro minimum inhibitory concentration and the in vivo 99% effective dose in mice, establishing in vitro and in vivo target engagement. Surprisingly, the lack of target engagement of the related ?-ketoacyl synthases (FabH and KasB) suggests a different mode of inhibition when compared with other Kas inhibitors of fatty acid biosynthesis in bacteria. These results clearly identify KasA as the biological target of GSK3011724A and validate this enzyme for further drug discovery efforts against tuberculosis.

SUBMITTER: Abrahams KA

PROVIDER: S-EPMC5025758 | biostudies-literature | 2016 Sep

REPOSITORIES: biostudies-literature

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Identification of KasA as the cellular target of an anti-tubercular scaffold.

Abrahams Katherine A KA Chung Chun-Wa CW Ghidelli-Disse Sonja S Rullas Joaquín J Rebollo-López María José MJ Gurcha Sudagar S SS Cox Jonathan A G JA Mendoza Alfonso A Jiménez-Navarro Elena E Martínez-Martínez María Santos MS Neu Margarete M Shillings Anthony A Homes Paul P Argyrou Argyrides A Casanueva Ruth R Loman Nicholas J NJ Moynihan Patrick J PJ Lelièvre Joël J Selenski Carolyn C Axtman Matthew M Kremer Laurent L Bantscheff Marcus M Angulo-Barturen Iñigo I Izquierdo Mónica Cacho MC Cammack Nicholas C NC Drewes Gerard G Ballell Lluis L Barros David D Besra Gurdyal S GS Bates Robert H RH

Nature communications 20160901

Phenotypic screens for bactericidal compounds are starting to yield promising hits against tuberculosis. In this regard, whole-genome sequencing of spontaneous resistant mutants generated against an indazole sulfonamide (GSK3011724A) identifies several specific single-nucleotide polymorphisms in the essential Mycobacterium tuberculosis β-ketoacyl synthase (kas) A gene. Here, this genomic-based target assignment is confirmed by biochemical assays, chemical proteomics and structural resolution of ...[more]

PMID: 27581223

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Project description:Indole-containing small molecules have been reported to have diverse pharmacological activities. The aromatic heterocyclic scaffold, which resembles various protein structures, has received attention from organic and medicinal chemists. Exploration of indole derivatives in drug discovery has rapidly yielded a vast array of biologically active compounds with broad therapeutic potential. Nature is the major source of indole scaffolds, but various classical and advanced synthesis methods for indoles have also been reported. One-pot synthesis is widely considered an efficient approach in synthetic organic chemistry and has been used to synthesize some indole compounds. The rapid emergence of drug-resistant tuberculosis is a major challenge to be addressed. Identifying novel targets and drug candidates for tuberculosis is therefore crucial. Researchers have extensively explored indole derivatives as potential anti-tubercular agents or drugs. Indole scaffolds containing the novel non-covalent (decaprenylphosphoryl-β-D-ribose2'-epimerase) DprE1 inhibitor 1,4-azaindole is currently in clinical trials to treat Mycobacterium tuberculosis. In addition, DG167 indazole sulfonamide with potent anti-tubercular activity is undergoing early-stage development in preclinical studies. Indole bearing cationic amphiphiles with high chemical diversity have been reported to depolarize and disrupt the mycobacterial membrane. Some indole-based compounds have potential inhibitory activities against distinct anti-tubercular targets, including the inhibition of cell wall synthesis, replication, transcription, and translation, as summarized in the graphical abstract. The success of computer-aided drug design in the fields of cancer and anti-viral drugs has accelerated in silico studies in antibacterial drug development. This review describes the sources of indole scaffolds, the potential for novel indole derivatives to serve as anti-tubercular agents, in silico findings, and proposed actions to facilitate the design of novel compounds with anti-tubercular activity.

Project description:Mycobacterium tuberculosis remains one of the world's contributors to mortality. With the emergence of SARS-CoV-2 coinfections, patients with TB are predisposed to being more heavily weighed down by COVID-19 disease and its opportunistic coinfections. The severity of the disease coupled with drug resistance on the currently used drugs warrants for the search for alternative remedies from synthetic agents, semisynthetics and natural products that include plants. Africa is rich in plant diversity with a promise as sources of drug agents, one of which is Eichhornia crassipes. This work aimed at isolating a fatty acid and dock it to β-ketoacyl-ACP synthase for possible anti-TB drug development prospects using computational tools. (9z,12z)-Octadeca-9,12-dienoic acid was isolated from Eichhornia crassipes for the first time using chromatographic techniques and identified using 1D and 2D NMR spectroscopic methods (1H NMR, COSY, HSQC, HMBC and 13C NMR). The compound was then docked to β-ketoacyl-ACP synthase (KasA), an essential member of the b-ketoacyl synthases encoded in the M. tuberculosis genome in comparison with its co-crystallized ligand JSF-3285, also for the first time. (9z,12z)-Octadeca-9,12-dienoic acid interacted with only phenylalanine239 and proline201 while JSF-3285 interacted with proline201, glutamine120, alanine119, leucine116, glutamine199, histadine345, phenylalanine239, glycine240 and glycine200. (9z,12z)-Octadeca-9,12-dienoic acid had a ligand efficiency of 0.24, compared to the co-crystallized ligand's 0.36. The compound was too flexible and elongated with -4.72 KCalmol-1 binding energy. Despite some unfavourable physico-chemical properties, the compound still provides reliable interactions that only require logical structural modifications by the addition of polar regions amongst others to increase interactions and ligand efficiency, which can consequently stand to be a better potential drug lead. For the first time, plant-based (9z,12z)-Octadeca-9,12-dienoic acid isolated from Eichhornia crassipes was shown to interact fairly well with β-ketoacyl-ACP synthase and proved to be a potential starting material from which anti-tubercular drugs can be designed.

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Identification of KasA as the cellular target of an anti-tubercular scaffold.

Publications

Identification of KasA as the cellular target of an anti-tubercular scaffold.

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