Flavanones: A potential natural inhibitor of the ATP binding site of PknG of Mycobacterium tuberculosis

Protein kinase G-a key regulator of pathogenesis in Mycobacterium tuberculosis infection

Mycobacterium tuberculosis (M. tuberculosis), the causative agent of tuberculosis (TB), remains a leading global health threat, exacerbated by rising drug resistance and the ability of this pathogen to persist within host macrophages. Central to the intracellular survival of M. tuberculosis is Protein Kinase G (PknG), a secreted, eukaryotic-like serine/threonine kinase that subverts host immune defenses and modulates bacterial physiology. This review provides a comprehensive overview of structural features and the multifaceted role of PknG in M. tuberculosis pathogenesis, including inhibition of phagosome-lysosome fusion, acid tolerance, metabolic reprogramming, autophagy suppression, and cell wall remodelling. Additionally, we discuss recent advancements in targeting PknG with small-molecule inhibitors, highlighting its promise as a therapeutic target. By delineating PknG's central role in host-pathogen interactions and stress adaptation, this review underscores its potential in shaping future anti-TB strategies, especially against drug-tolerant and latent infections..

Molecular docking, free energy calculations, ADMETox studies, DFT analysis, and dynamic simulations highlighting a chromene glycoside as a potential inhibitor of PknG in Mycobacterium tuberculosis

Introduction

Tuberculosis (TB), caused by the Mycobacterium tuberculosis (M.tb), remains a serious medical concern globally. Resistant M.tb strains are emerging, partly because M.tb can survive within alveolar macrophages, resulting in persistent infection. Protein kinase G (PknG) is a mycobacterial virulence factor that promotes the survival of M.tb in macrophages. Targeting PknG could offer an opportunity to suppress the resistant M.tb strains.

Methods

In the present study, multiple computational tools were adopted to screen a library of 460,000 molecules for potential inhibitors of PknG of M.tb.

Results and discussions

Seven Hits (1-7) were identified with binding affinities exceeding that of the reference compound (AX20017) towards the PknG catalytic domain. Next, the ADMETox studies were performed to identify the best hit with appropriate drug-like properties. The chromene glycoside (Hit 1) was identified as a potential PknG inhibitor with better pharmacokinetic and toxicity profiles rendering it a potential drug candidate. Furthermore, quantum computational analysis was conducted to assess the mechanical and electronic properties of Hit 1, providing guidance for further studies. Molecular dynamics simulations were also performed for Hit 1 against PknG, confirming the stability of its complex. In sum, the findings in the current study highlight Hit 1 as a lead with potential for development of drugs capable of treating resistant TB.

The Potential of Magnolia spp. in the Production of Alternative Pest Control Substances

The irrational use of synthetic pesticides in agriculture has had negative impacts on ecosystems and contributed to environmental pollution. Botanical pesticides offer a clean biotechnological alternative to meet the agricultural challenges posed by pests and arthropods. This article proposes the use of fruit structures (fruit, peel, seed, and sarcotesta) of several Magnolia species as biopesticides. The potential of extracts, essential oils, and secondary metabolites of these structures for pest control is described. From 11 Magnolia species, 277 natural compounds were obtained, 68.7% of which were terpenoids, phenolic compounds, and alkaloids. Finally, the importance of a correct management of Magnolia species to ensure their sustainable use and conservation is stressed.

Bacterial effector kinases and strategies to identify their target host substrates

Post-translational modifications (PTMs) are critical in regulating protein function by altering chemical characteristics of proteins. Phosphorylation is an integral PTM, catalyzed by kinases and reversibly removed by phosphatases, that modulates many cellular processes in response to stimuli in all living organisms. Consequently, bacterial pathogens have evolved to secrete effectors capable of manipulating host phosphorylation pathways as a common infection strategy. Given the importance of protein phosphorylation in infection, recent advances in sequence and structural homology search have significantly expanded the discovery of a multitude of bacterial effectors with kinase activity in pathogenic bacteria. Although challenges exist due to complexity of phosphorylation networks in host cells and transient interactions between kinases and substrates, approaches are continuously being developed and applied to identify bacterial effector kinases and their host substrates. In this review, we illustrate the importance of exploiting phosphorylation in host cells by bacterial pathogens via the action of effector kinases and how these effector kinases contribute to virulence through the manipulation of diverse host signaling pathways. We also highlight recent developments in the identification of bacterial effector kinases and a variety of techniques to characterize kinase-substrate interactions in host cells. Identification of host substrates provides new insights for regulation of host signaling during microbial infection and may serve as foundation for developing interventions to treat infection by blocking the activity of secreted effector kinases.

Identifying RO9021 as a Potential Inhibitor of PknG from Mycobacterium tuberculosis: Combinative Computational and In Vitro Studies

Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis (Mtb). Despite being considered curable and preventable, the increase of antibiotic resistance is becoming a serious public health problem. Mtb is a pathogen capable of surviving in macrophages, causing long-term latent infection where the mycobacterial serine/threonine protein kinase G (PknG) plays a protective role. Therefore, PknG is an important inhibitory target to prevent Mtb from entering the latency stage. In this study, we use a pharmacophore-based virtual screening and biochemical assays to identify the compound RO9021 (CHEMBL3237561) as a PknG inhibitor. In detail, 1.5 million molecules were screened using a scalable cloud-based setup, identifying 689 candidates, which were further subjected to additional screening employing molecular docking. Molecular docking spotted 62 compounds with estimated binding affinities of -7.54 kcal/mol (s.d. = 0.77 kcal/mol). Finally, 14 compounds were selected for in vitro experiments considering previously reported biological activities and commercial availability. In vitro assays of PknG activity showed that RO9021 inhibits the kinase activity similarly to AX20017, a known inhibitor. The inhibitory effect was found to be dose dependent with a relative IC₅₀ value of 4.4 ± 1.1 μM. Molecular dynamics simulations predicted that the PknG-RO9021 complex is stable along the tested timescale. Altogether, our study indicates that RO9021 is a noteworthy drug candidate for further developing new anti-TB drugs that hold excellent reported pharmacokinetic parameters.