A Therapeutic Role for the F1FO-ATP Synthase

Recently, the F₁F_O-ATP synthase, due to its dual role of life enzyme as main adenosine triphosphate (ATP) maker and of death enzyme, as ATP dissipator and putative structural component of the mitochondrial permeability transition pore (mPTP), which triggers cell death, has been increasingly considered as a drug target. Accordingly, the enzyme offers new strategies to counteract the increased antibiotic resistance. The challenge is to find or synthesize compounds able to discriminate between prokaryotic and mitochondrial F₁F_O-ATP synthase, exploiting subtle structural differences to kill pathogens without affecting the host. From this perspective, the eukaryotic enzyme could also be made refractory to macrolide antibiotics by chemically produced posttranslational modifications. Moreover, because the mitochondrial F₁F_O-ATPase activity stimulated by Ca²⁺ instead of by the natural modulator Mg²⁺ is most likely involved in mPTP formation, effectors preferentially targeting the Ca²⁺-activated enzyme may modulate the mPTP. If the enzyme involvement in the mPTP is confirmed, Ca²⁺-ATPase inhibitors may counteract conditions featured by an increased mPTP activity, such as neurodegenerative and cardiovascular diseases and physiological aging. Conversely, mPTP opening could be pharmacologically stimulated to selectively kill unwanted cells. On the basis of recent literature and promising lab findings, the action mechanism of F₁ and F_O inhibitors is considered. These molecules may act as enzyme modifiers and constitute new drugs to kill pathogens, improve compromised enzyme functions, and limit the deathly enzyme role in pathologies. The enzyme offers a wide spectrum of therapeutic strategies to fight at the molecular level diseases whose treatment is still insufficient or merely symptomatic.

Structure-Function Mutational Analysis and Prediction of the Potential Impact of High Risk Non-Synonymous Single-Nucleotide Polymorphism on Poliovirus 2A Protease Stability Using Comprehensive Informatics Approaches

Polio viral proteinase 2A performs several essential functions in genome replication. Its inhibition prevents viral replication, thus making it an excellent substrate for drug development. In this study, the three-dimensional structure of 2A protease was determined and optimized by homology modelling. To predict the molecular basis of the interaction of small molecular agonists, docking simulations were performed on a structurally diverse dataset of poliovirus 2A protease (PV2A^pr°) inhibitors. Docking results were employed to identify high risk missense mutations that are highly damaging to the structure, as well as the function, of the protease. Intrinsic disorder regions (IDRs), drug binding sites (DBS), and protein stability changes upon mutations were also identified among them. Our results demonstrated dominant roles for Lys 15, His 20, Cys 55, Cys 57, Cys 64, Asp 108, Cys 109 and Gly 110, indicating the presence of various important drug binding sites of the protein. Upon subjecting these sites to single-nucleotide polymorphism (SNP) analysis, we observed that out of 155 high risk SNPs, 139 residues decrease the protein stability. We conclude that these missense mutations can affect the functionality of the 2A protease, and that identified protein binding sites can be directed for the attachment and inhibition of the target proteins.

The molecular interaction of the high affinity reversal agent XR9576 with P-glycoprotein

1 The kinetics and nature of equilibrium binding were used to characterize the molecular interaction of the anthranilic acid derivative [3H]-XR9576 with the multidrug resistance P-glycoprotein (P-gp). XR9576 displayed specific high-affinity binding to P-gp (Bmax = 275 pmol mg-1, Kd = 5.1 nM). The transport substrates [3H]-vinblastine and [3H]-paclitaxel displayed 4 fold and 20 fold lower affinity respectively for P-gp. The duration of action of XR9576 with P-gp was increased in comparison to that of vinblastine which displayed a slower rate of association and a faster dissociation rate. 2 The relative affinities of several modulators and transport substrates to interact with P-gp were determined from displacement drug equilibrium binding assays. Vinblastine and paclitaxel could only fractionally displace [3H]-XR9576 binding, displaying Ki values significantly different from their measured Kd values. This suggests a non-competitive interaction between XR9576 and the P-gp substrates vinblastine and paclitaxel. 3 XR9576 was shown to be a potent modulator of P-gp mediated [3H]-vinblastine and [3H]-paclitaxel transport as it increased the steady-state accumulation of these cytotoxics in CHrB30 cells to levels observed in non-P-gp-expressing AuxB1 cells (EC50 = 487+/-50 nM). This inhibition of drug transport is not mediated through competition for transport since [3H]-XR9576 accumulation was not influenced by P-gp expression or function. 4 These results demonstrate that the P-gp modulator XR9576 exhibits greater selectivity, duration of inhibition and potency of interaction with this transporter than any other reported modulators. Several lines of evidence suggest that XR9576 inhibits P-gp function by binding at a site which is distinct from the site of interaction of transport substrates. The two sites may be classified as serving modulatory or transport functions.