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SPRY domain- and SOCS box-containing proteins SPSB1, SPSB2, and SPSB4 interact with inducible nitric oxide synthase (iNOS), causing the iNOS to be polyubiquitinated and targeted for degradation. Inhibition of this interaction increases iNOS levels, and consequently cellular nitric oxide (NO) concentrations, and has been proposed as a potential strategy for killing intracellular pathogens. We previously described two DINNN-containing cyclic peptides (CP1 and CP2) as potent inhibitors of the murine SPSB-iNOS interaction. In this study, we report the crystal structures of human SPSB4 bound to CP1 and CP2 and human SPSB2 bound to CP2. We then used these structures to design a new inhibitor in which an intramolecular hydrogen bond was replaced with a hydrocarbon linkage to form a smaller macrocycle while maintaining the bound geometry of CP2 observed in the crystal structures. This resulting pentapeptide SPSB-iNOS inhibitor (CP3) has a reduced macrocycle ring size, fewer nonbinding residues, and includes additional conformational constraints. CP3 has a greater affinity for SBSB2 ( K

Nitric oxide (NO) is an important effector molecule in host defence against bacterial pathogens. The development of fluorescence imaging to monitor NO production in vitro and in vivo will increase our understanding of its biological role. Recently, a novel 'trappable' fluorescent blue 'turn-on' Cu(II)-complexed coumarin-based probe (CB) has been developed to detect NO. In this study, CB was investigated to evaluate its ability to detect NO in macrophages. Using confocal microscopy, NO was successfully detected in macrophages in the presence of stimuli that induce nitric oxide synthase (iNOS), the enzyme responsible for production of NO. The time dependence and subcellular compartmentalisation of CB in macrophages were evaluated. The probe can be trapped within cells and reacts directly and specifically with NO, rendering it a promising tool for imaging NO in response to pharmacological agents that modulate its level, for example during bacterial infections.

Grafting bioactive peptide sequences onto small cysteine-rich scaffolds is a promising strategy for enhancing their stability and value as novel peptide-based therapeutics. However, correctly folded disulfide-rich peptides can be challenging to produce by either recombinant or synthetic means. The single disulfide-directed β-hairpin (SDH) fold, first observed in contryphan-Vc1, provides a potential alternative to complex disulfide-rich scaffolds. We have undertaken recombinant production of full-length contryphan-Vc1 (rCon-Vc1[Z1Q]) and a truncated analogue (rCon-Vc11–22[Z1Q]), analyzed the backbone dynamics of rCon-Vc1[Z1Q], and probed the conformational and proteolytic stability of these peptides to evaluate the potential of contryphan-Vc1 as a molecular scaffold. Backbone 15N relaxation measurements for rCon-Vc1[Z1Q] indicate that the N-terminal domain of the peptide is ordered up to Thr19, whereas the remainder of the C-terminal region is highly flexible. The solution structure of truncated rCon-Vc11–...

Based on the hit structures that have been identified in our previous studies against EGFR and HER2, new potential inhibitors that share the same scaffold of the hit structures are designed and screened in silico. Insights into understanding the potential inhibitory effect of the new inhibitors against both EGFR and HER2 receptors is obtained using extended molecular dynamics (MD) simulations and different scoring techniques. The binding mechanisms and dynamics are detailed with respect to two approved inhibitors against EGFR (lapatinib) and HER2 (SYR127063). The best scoring inhibitor (T9) is chosen for additional in silico investigation against both the wild-type and T790M mutant strain of EGFR and the wild-type HER2. The results reveal that certain substitution patterns increase the stability and assure stronger binding and higher H-bond occupancy of the conserved water molecule that is commonly observed with kinase crystal structures. Furthermore, the new inhibitor (T9) forms stable interactions with the mutant strain as a direct consequence of the enhanced ability to form additional hydrogen bonding interactions with binding site residues.

In the development of new anti-cancer drugs to tackle the problem of resistance to current chemotherapeutic agents, a new series of anti-HER2 (human epidermal growth factor receptors 2) agents has been synthesized and investigated using different computational methods. Although non-selective, the most active inhibitor in the new series shows higher activity toward HER2 than EGFR. The induced fit docking protocol (IFD) is performed to find possible binding poses of the new inhibitors in the active site of the HER2 receptor. Molecular dynamic simulations of the inhibitor–protein complexes for the two most active compounds from the new series are carried out. Simulations stability is checked using different stability parameters. Different scoring functions are employed.

Herein, we designed and synthesized certain anilinoquinazoline derivatives bearing bulky arylpyridinyl, arylpropenoyl and arylpyrazolyl moieties at the 4' position of the anilinoquinazoline, as potential dual HER2/EGFR kinase inhibitors. A detailed molecular modeling study was performed by docking the synthesized compounds in the active site of the epidermal growth factor receptor (EGFR). The synthesized compounds were further tested for their inhibitory activity on EGFR and HER2 tyrosine kinases. The aryl 2-imino-1,2-dihydropyridine derivatives 5d and 5e displayed the most potent inhibitory activity on EGFR with IC50 equal to 2.09 and 1.94 μM, respectively, and with IC50 equal to 3.98 and 1.04 μM on HER2, respectively. Furthermore, the anti-proliferative activity of these most active compounds on MDA-MB-231 breast cancer cell lines, known to overexpress EGFR, showed an IC50 range of 2.4 and 2.5 μM, respectively.