Aberrant JNK signaling can result in two main forms of disease in humans: 1) neurological, coronary, hepatobiliary, and respiratory diseases and 2) autoimmune, inflammatory, and cancer conditions. Enantiomers of the lignan zuonin A, (-)-zuonin A and (+)-zuonin A, have been shown to bind to JNK isoforms with similar affinity and disrupt protein-protein interactions at JNK's D-recruitment site, making them a good candidate for specific non-ATP competitive inhibitors. However, (-)-zuonin A inhibits 80% of JNK catalyzed reactions at saturating levels, while (+)-zuonin A only inhibits 15%. Molecular docking and molecular dynamics simulations were performed to gain a better understanding of how these inhibitors interact JNK. The results of this study provide an alternative binding mode for (-)-zuonin A, compared to one proposed in a previous study, that shows (-)-zuonin A interacting with JNK via an induced fit mechanism by forming a larger pocket for itself near the highly conserved [phi]A-X-[phi]B recognition site, a dynamic move not seen in (+)-zuonin A simulations, and may help explain their different inhibition patterns. / text

The enzymes acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are inhibited by nerve agents such as sarin and tabun. In general, the inhibited enzymes are reactivated by bisquaternary ammonium compounds (oximes). The binding free energies of the oximes; 2-PAM, MMB-4, HI-6, and obidoxime bound to human AChE (hAChE) and human BChE (hBChE) inhibited by sarin and tabun and also to the uninhibited enzymes were calculated using various computational methods. Using thermodynamic integration, the binding free energies of all the inhibited and uninhibited systems of MMB-4 and obidoxime were evaluated. The standard binding free energies (dA) were more negative than the experimental values due to limitations of the ff99 forcefield. The RMS error of dA for the inhibited systems of MMB-4 was 2.1 kcal/mol, and for obidoxime systems it was 4.8 kcal/mol with respect to the experimental free energies. The binding enthalpies calculated using MM-GBSA and MM-PBSA methods for 2-PAM, MMB-4, HI-6, and obidoxime systems were negative, except for hBChE-sarin-MMB-4 and hBChE-sarin-obidoxime. For all the systems the TdS values calculated using normal mode analysis were equal to or lower in magnitude than their corresponding binding enthalpies. As a result, the estimated free energies were positive for most of the systems. Clearly, the present algorithms cannot effectively estimate the binding entropies for a protein-ligand system. Met81 has commonly shown favorable interactions, and lysine or arginine exhibited unfavorable interactions with the reactivator in all the systems. Second, the interactions between chloropyrifos-oxon (Cpo) and experimentally tested neutral and monopyridinium oximes bound to the Q192 or R192 polymorphs of human paraoxonase1 (hPON1) were studied. The equilibrated Q192 and R192 hPON1 were structurally different than the crystal structure of recombinant PON1. The neutral oximes have shown more favorable interactions with Cpo in Q192 hPON1 + Cpo system compared to R192 hPON1 + Cpo. Whereas the monopyridinium oximes interacted more affectively with Cpo in R192 hPON1 than Q192 hPON1. The relative deprotonation energy of the monopyridinium oxime was lower than the neutral oxime. Hence, the monopyridinium oxime can hydrolyze an organophosphate at a higher rate than a neutral oxime.