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Catálisis ácido-base general en el mecanismo de una ribozima ribozima del virus de la hepatitis delta
S Nakano1, D M Chadalavada, P C Bevilacqua
1Department of Chemistry, Pennsylvania State University, University Park, PA 16802, USA.
Science (New York, N.Y.)
|February 26, 2000
Resumen
Las enzimas de ARN, o ribozimas, pueden realizar una catálisis ácido-base general, similar a las enzimas de proteínas. La ribozima del virus de la hepatitis delta utiliza la citosina 75 (C75) como un ácido general, imitando la histidina.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Biología Molecular Biología Molecular
- La catálisis del ARN.
Sus antecedentes:
- Las enzimas proteicas utilizan la catálisis ácido-base general para mejorar la velocidad de reacción.
- La pK (a) de la histidina cerca del pH fisiológico la optimiza para este papel catalítico.
- Las enzimas de ARN (ribozimas) también poseen capacidades catalíticas.
Objetivo del estudio:
- Para investigar el mecanismo catalítico de la ribozima del virus de la hepatitis delta.
- Para identificar el ácido y la base generales en la reacción de auto-escisión de la ribozima.
- Para explorar el papel de la citosina 75 (C75) en la catálisis de la ribozima.
Principales métodos:
- Análisis de los perfiles de reactividad-pH en diferentes concentraciones de cationes.
- Examen de la distancia entre C75 y el oxígeno del grupo saliente.
- Caracterización del pK (a) del C75 y su modulación por iones metálicos.
Principales resultados:
- La citosina 75 (C75) actúa como el catalizador ácido general en la autodescisión de la ribozima.
- El hidróxido de metal hidratado ligado a la ribozima funciona como la base general.
- C75 exhibe una pK(a) perturbada a la neutralidad, que se asemeja a las propiedades catalíticas de la histidina.
- Una interacción anticooperativa entre el C75 protonado y los iones metálicos modula la pK del C75 (a).
Conclusiones:
- La catálisis ácido-base general es un mecanismo funcional para las enzimas de ARN.
- La ribozima del virus de la hepatitis delta emplea una estrategia catalítica "semejante a la histidina" a través de C75.
- Esto amplía el conocido repertorio catalítico del ARN, potencialmente aumentando las tasas de reacción.
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