Africa accounts for the majority of HIV-1 infections worldwide caused mainly by the A and C viral subtypes rather than B subtype, which prevails in the United States and Western Europe. In Brazil, B subtype is the major subtype, but F, C, and A also circulate. These non-B subtypes present polymorphisms, and some of them occur at sites that have been associated with drug resistance, including the HIV-1 protease (PR), one important drug target. Here, we report a Molecular Dynamics study of the B and non-B PR complexed with the inhibitor ritonavir to delineate the behavior of each subtype. We compare root mean squared deviation, binding free energy by linear interaction energy approach, hydrogen bonds, and intermolecular contact surface area between inhibitor and PR. From our results, we can provide a basis to understand the molecular mechanism of drug resistance in non-B subtypes. In this sense, we found a decrease of approx 4 kcal/mol in deltaG of binding between B and non-B subtypes. This corresponds to the loss of one hydrogen bond, which is in agreement with our H-bond analysis. Previous experimental affinity studies reported analogous results with inhibition constant values for non-B PR.

Reativadores eficientes de Aceticolinesterase são fundamentais para o desenvolvimento de antídotos contra o envenenamento por pesticidas neurotóxicos e agentes de guerra química. Todavia, o mecanismo da reação de reativação e as características estruturais dos reativadores conhecidos são pouco compreendidos. Com o objetivo de estudar o comportamento dinâmico e o efeito da carga líquida do antídoto na reativação desta enzima, foi conduzido um estudo por dinâmica molecular da acetilcolinesterase humana inibida por tabun em complexo com o antídoto pralidoxima e com seu análogo deazapralidoxima nas formas neutra e aniônica. Os resultados mostraram que a carga positiva da pralidoxima é importrante para sua admissão e permanência dentro do sítio ativo. Além disso, os análogos, diferente da pralidoxima, quando colocados dentro do sítio ativo, se distanciam do resíduo serina fosforilado da enzima e são repelidos pelo potencial eletrostático na entrada do canal que conduz ao sítio ativo.Efficient acetylcholinesterase reactivators are fundamental for the development of antidotes against poisoning by neurotoxic pesticides and chemical warfare agents. However, the mechanism of the reactivation reaction and the structural characteristics of the known reactivators are poorly understood. In order to study the dynamic behavior and the effect of the antidote net charge in the reactivation of this enzyme, we carried out a molecular dynamics study of human acetylcholinesterase inhibited by tabun in complex with the antidote pralidoxime and with its deaza analogues in the neutral and anionic forms. Results show that the positive charge of pralidoxime is important for its admission and permanence inside the active site. Also, the analogues, unlike pralidoxime, when forced inside the active site, move away from the phosphorilated serine residue of the enzyme and are repelled by the electrostatic potential at the entrance of the channel that conducts to the active site. Keywords: acetylcholinesterase, molecular dynamics, tabun, antidotes, neurotoxic agents IntroductionThe intensive use of neurotoxic organophosphorous compounds as pesticides in agriculture, as well as their potential use as mass destruction agents in chemical warfare, has attracted attention to the development of efficient antidotes for this type of poisoning.1,2 However, the knowledge on the appropriate treatment for patients exposed to this kind of compounds is limited to few groups of physicians around the world. 1,2One particularly important family of lethal tactical warfare chemicals is the group known as the nerve agents, which are closely related in chemical structure and biological action to many commonly used organophosphorous insecticides, but which are much more lethal. 1,2The nerve agents are esters of phosphoric acid and are potent inhibitors of acetylcholinesterase, a fundamental enzyme for ending nervous impulses. These compounds inhibit all acetylcholinesterases, including the human enzyme (HuAChE), by phosphorylating a serine hydroxyl group (Ser203 in ...

A Serina Hidroximetiltransferase de Plasmodium falciparum nunca foi vista como alvo para a quimioterapia antimalarial, possivelmente devido a sua grande similaridade seqüencial com a enzima humana. Esta similaridade sugere que este parasita pode ser incapaz de mutar esta enzima para desenvolver resistência à quimioterapia. Neste trabalho, diferenças observadas no comportamento dinâmico dos sítios ativos da estrutura cristalográfica da enzima humana e um modelo, por homologia, da enzima do parasita, ambos complexados com glicina, como N-glicina-[3-hidróxi-2-metil-5-fosfonooximetil-piridin-4-il-metano], e ácido 5-formil-6-hidrofólico, foram utilizadas para o planejamento de inibidores seletivos desta enzima como novos potenciais antimalariais. Estes potenciais inibidores são derivados do ácido 5-formil-6-hidrofólico com diferentes cargas e comprimentos de cauda. Simulações por dinâmica molecular e estimativas das energias de interação dos compostos nos sítios ativos de ambas as enzimas mostraram que os compostos com carga líquida negativa e caudas curtas ou caudas longas e anfóteras, seriam potencialmente mais seletivos em relação à enzima do parasita.Plasmodium falciparum Serine Hydroxymethyltransferase has never been used as target for antimalarial chemotherapy, possibly because its great sequence similarity with the human enzyme. This similarity suggests implies that P. falciparum may not be able to mutate this enzyme to develop resistance for chemotherapy. In this work, we have used differences on the dynamic behavior of the active sites of the crystallographic structure of the human enzyme and a homology model of parasite's enzyme, both in complex with glycine, as N-glycine-[3-hydroxy-2-methyl-5-phosphonooxymethyl-pyridin-4-yl-methane] and 5-formyl-6-hydrofolic acid, to design prototypes for selective inhibitors of this enzyme as new potential antimalarials. Those potential inhibitors are 5-formyl-6-hydrofolic acid derivatives with different charges and tail lengths. Molecular dynamics simulations and interaction energy estimates of the compounds within the active sites of both enzymes showed that compounds with a negative net charge and either shorter tails or longer amphoteric tails, would be more selective towards pfSHMT.

Motivation The generation of parameter files for molecular dynamics (MD) simulations of small molecules that are suitable for force fields commonly applied to proteins and nucleic acids is often challenging. The ACPYPE software and website aid the generation of such parameter files. Results ACPYPE uses OpenBabel and ANTECHAMBER to generate MD input files in Gromacs, AMBER, CHARMM, and CNS formats. It can now take a SMILES string as input, in addition to the original PDB or mol2 coordinate files, with GAFF2 support and GLYCAM force field conversion added. It can be installed locally via Anaconda, PyPI, and Docker distributions, while the web server at https://bio2byte.be/acpype/ was updated with an API, and provides visualization of results for uploaded molecules as well as a pre-generated set of 3738 drug molecules. Availability and implementation The web application is freely available at https://www.bio2byte.be/acpype/ and the open-source code can be found at https://github.com/alanwilter/acpype.

We have applied a theoretical methodology, previously developed to evaluate the association and kinetic reactivation constants of oximes, comparing theoretical data obtained for human acetylcholinesterase (HsAChE) with in vitro results from Mus musculus AChE (MmAChE) previously reported in the literature. Our results, further checked by additional molecular dynamics simulations steps, showed a good correlation between the theoretical and experimental data, supporting the methodology as appropriate for prediction of thermodynamic and kinetic parameters and corroborated MmAChE as a suitable model for studies with HsAChE.

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