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Site Directed Spin Labeling and EPR Spectroscopic Studies of Pentameric Ligand-Gated Ion Channels
Published on: July 4, 2016
Correlaciones de la estructura y las propiedades electrónicas de la espectroscopia EPR de la hidroxilamina
M P Hendrich1, D Petasis, D M Arciero
1Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA. hendrich@andrew.cmu.edu
Journal of the American Chemical Society
|July 18, 2001
Resumen
La hidroxilamina oxidorreductaza (HAO) utiliza ocho hemos para oxidar el NH(2) OH. Las simulaciones cuantitativas de EPR revelan una superposición electrónica directa entre hemes, lo que sugiere centros redox biológicos de dos electrones.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Microbiología Microbiología.
- Enzimología Enzimología.
Sus antecedentes:
- La hidroxilamina oxidorreductaza (HAO) es crucial para la nitrificación en Nitrosomonas europaea.
- La enzima contiene ocho hemos por subunidad involucrada en la catálisis y el transporte de electrones.
- Estudios anteriores observaron una disposición espacial única de estos hemisferios.
Objetivo del estudio:
- Para aclarar el acoplamiento electrónico y las funciones funcionales de los ocho hemes en HAO.
- Para asignar señales EPR específicas y potenciales de reducción a hemes individuales dentro de la estructura cristalina.
- Investigar el mecanismo de la comunicación electrónica entre hemisferios.
Principales métodos:
- Simulación cuantitativa de las señales de resonancia paramagnética electrónica (EPR).
- Análisis de la estructura cristalina de la hidroxilamina oxidorreducta.asa.
- Modelado computacional de las interacciones heme-heme.
Principales resultados:
- Acoplamientos de intercambio determinados y señales/potenciales de reducción asignados a hemisferios específicos.
- Identificó tres tipos de motivos de emparejamiento de diheme dentro de la estructura de la enzima.
- Se observa el acoplamiento electrónico entre al menos cuatro hemes, formando dos pares distintos.
- Un par hemo acoplado electrónicamente se encuentra en el sitio activo de la enzima.
- La evidencia sugiere que la superposición electrónica directa de los orbitales de la porfirina facilita las interacciones hemo-hemo.
Conclusiones:
- El arreglo único de hemo en HAO soporta la comunicación electrónica directa.
- Los pares de hemo funcionan como centros redox biológicos de dos electrones para una transferencia eficiente de electrones.
- Este hallazgo proporciona información sobre los mecanismos de transporte de electrones en las metalloenzimas.
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