Identification of Novel Inhibitors of Mycobacterium tuberculosis PknG Using Pharmacophore Based Virtual Screening, Docking, Molecular Dynamics Simulation, and Their Biological Evaluation

PknG is a Ser/thr protein kinase that plays a crucial role in regulatory processes within the mycobacterial cell and signaling cascade of the infected host cell. The essentiality of PknG in mycobacterial virulence by blocking phagosome–lysosome fusion as well as its role in intrinsic antibiotic resistance makes it an attractive drug target. However, only very few compounds have been reported as Mycobacterium tuberculosis PknG (<i>Mt</i>PknG) inhibitors so far. Therefore, in an effort to find potential inhibitors against <i>Mt</i>PknG, we report here a sequential pharmacophore-based virtual screening workflow, 3-fold docking with different search algorithms, and molecular dynamic simulations for better insight into the predicted binding mode of identified hits. After detailed analysis of the results, six ligands were selected for in vitro analysis. Three of these molecules showed significant inhibitory activity against <i>Mt</i>PknG. In addition, inhibitory studies of mycobacterial growth in infected THP-1 macrophages demonstrated considerable growth inhibition of M. bovis BCG induced through compound NRB04248 without any cytotoxic effect against host macrophages. Our results suggest that the compound NRB04248 can be explored for further design and optimization of <i>Mt</i>PknG inhibitors

Mycobacterial protein tyrosine kinase, PtkA phosphorylates PtpA at tyrosine residues and the mechanism is stalled by the novel series of inhibitors

<p>Phosphorylation and dephosphorylation are the key mechanisms for mycobacterial physiology and play critical roles in mycobacterial survival and in its pathogenesis. Mycobacteria evade host immune mechanism by inhibiting phagosome – lysosome fusion in which mycobacterial protein tyrosine phosphatase A (PtpA;TP) plays an indispensable role. Tyrosine kinase (PtkA;TK) activated by autophosphorylation; phosphorylates TP, which subsequently leads to increase in its phosphatase activity. The phosphorylated TP is secreted in phagosome of macrophage. In the present study, we have shown that the phosphorylation at two sites of TP; Y¹²⁸ and Y¹²⁹ are critical for TK-mediated phosphatase activity. The disruption of this interaction between TK and TP inhibits activation of later which further leads to the decrease in intracellular survival of mycobacteria. Furthermore, the proof of concept has been established using benzylbenzofurans and benzofuranamides, which inhibit the growth and intracellular survival of mycobacteria, associate with the functional sites of TP and contend with the TK. This binding was further restated by looking at the anchorage of protein–protein and the protein–inhibitor complexes in the homology-based structure models and by surface plasmon resonance analysis.</p

Identification of 1‑[4-Benzyloxyphenyl)-but-3-enyl]‑1<i>H</i>‑azoles as New Class of Antitubercular and Antimicrobial Agents

A series of 1-[(4-benzyloxyphenyl)-but-3-enyl]-1<i>H-</i>azoles has been identified as potent antitubercular agents against <i>Mycobacterium tuberculosis</i>. Synthesis of compounds involved acid catalyzed ring-opening of cyclopropyl ring of phenyl cyclopropyl methanols followed by nucleophilic attack of the azoles on the carbocation intermediates. Several of the compounds <b>26</b>, <b>34</b>, and <b>36</b> exhibited significant antitubercular activities with MIC value as low as 1.56, 1.56, and 0.61 μg/mL, respectively, comparable to many standard drugs. These compounds were also screened against other strains of bacteria and fungi, and few of them showed good antifungal activity against <i>A. fumigatus</i>, responsible for lung infection