Estudio de la interacción molecular de donadores de óxido nítrico (NO) y donadores de nucleótidos cíclicos con el CNBD del canal HCN

• Autores: Violeta Rangel
• Directores de la Tesis: Francisco Javier Melendez Bustamante (dir. tes.), María Eugenia Castro Sánchez (dir. tes.)
• Lectura: En la Benemérita Universidad Autónoma de Puebla (BUAP) ( México ) en 2020
• Idioma: español
• Enlaces
  • Tesis en acceso abierto en: hdl.handle.net
• Resumen
  • español

    “Los canales HCN (Hyperpolarization-actived Cyclic Nucleotide-gated channels) son proteínas de membrana responsables de la actividad eléctrica de las células excitables. Además, son activados por hiperpolarización y regulados por unión a nucleótidos cíclicos y óxido nítrico (NO). Para estudiar el mecanismo de descomposición del NO es necesario contar con compuestos que liberen NO a los sistemas biológicos. Las sales de diazeniumdiolato (NONOatos) constituyen una clase versátil de donadores de NO y debido a que este mecanismo sigue siendo de interés, en esta tesis se describe el mecanismo de liberación del NO a partir de NONOatos mediante un enfoque teórico basado en la teoría del funcional de la densidad (DFT), para después evaluar los sitios de interacción de los ligantes con el dominio de unión a nucleótido cíclico (CNBD) del canal HCN mediante simulaciones de dinámica molecular. Nuestra propuesta de mecanismo de liberación de NO surge del estudio de protonación en los NONOatos (1-5). Se evaluó el papel del tamaño del sustituyente dialquilamino en la estructura de los NONOatos (15) y se observó que los tautómeros protonados (H1H5) están involucrados en la generación de los productos. Se propuso que el tautómero 1-5-H5, protonado en el nitrógeno del amino del grupo diolato, genera el estado de transición para llevar a cabo el mecanismo.”

  • English

    The Hyperpolarization-actived Cyclic Nucleotid-gated channels (HCN) basically are proteins embedded in the membrane responsible for the electric activity of excitable cells. They are activated by membrane hyperpolarization and regulated by the binding to cyclic nucleotides and nitric oxide (NO). In order to carry out the interaction mechanism between HCN channels and the ligands, it is necessary to have compounds that can supply concentrations of NO to biological systems. The diazeniumdiolate salts (NONOates) constituent a versatile class of NO donor. In this work, the mechanism of NO release from NONOate is described, using DFT theoretical calculations. The interaction sites of the ligands with the Cyclic Nucleotide Binding Domain (CNBD) of the HCN channel using molecular dynamics simulations were also studied. Our mechanism proposal starts from the protonation the NONOate (1-5). The possible protonated tautomers (H1-H5) from (1-5) are involved in the generation of the products. The 1-5-H5 tautomer (compound with the smallest size of dialkylamine substituent), which contains the proton on amino nitrogen, was proposed to be the appropriate transition state structure to carry out the NO release mechanism. The results show that the free energy of hydration value of the protonated tautomer H5 for all NONOates is the most labile reagent for releasing of NO. The 1-H5 tautomer presents the smallest energy barrier for exothermic dissociation generating a secondary amine and two NO molecules. On the other hand, the interactions and conformational consequences of the cyclic nucleotides, cAMP and cGMP, in the C-terminal domain (CNBD) of the HCN channels were investigated by molecular dynamics simulations. The CNBD of the HCN1 channel was studied in three conditions:

    CNBD (apoprotein), CNBD/cAMP, and CNBD/cGMP in the absence of the TM domain. The results of the simulations suggest that the movement of the apoprotein is characterized by significant localized fluctuations in the entrance of the cyclic nucleotide binding. In the presence of any of the ligands, those fluctuations are significantly reduced, which is consistent with observations reported in the literature.