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Estructura cristalina de un grupo I dominio de la ribozima: principios del empaque del ARN

J H Cate¹, A R Gooding, E Podell

¹Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA. doudna@csb.yale.edu

Science (New York, N.Y.)

|September 20, 1996

Resumen

El dominio P4-P6 de los intrones autodesconectados del Grupo I, crucial para la catálisis del ARN, tiene su estructura cristalina revelada. Esto revela el complejo empaquetado de ARN esencial para la función de la ribozima, el espliceosoma y el ribosoma.

Área de la Ciencia:

Biología Molecular Biología Molecular
Biología Estructural Biología estructural.
La bioquímica es la bioquímica.

Sus antecedentes:

Los intrones autoesplicantes del grupo I son ARN catalíticos (ribozimas) que se excisan a sí mismos de las moléculas de ARN precursoras.
Esta actividad catalítica implica una reacción de transesterificación en dos pasos.
La ribozima funcional comprende dos dominios estructurales, siendo el dominio P4-P6 un componente clave.

Objetivo del estudio:

Determinar la estructura cristalina de alta resolución del dominio P4-P6 del intrón del grupo I de la Tetrahymena thermophila.
Para aclarar la base estructural de la actividad catalítica y la estabilidad de este dominio de la ribozima.
Comprender los principios del plegamiento y empaquetado del ARN en grandes complejos de ribonucleoproteínas.

Principales métodos:

Se empleó cristalografía de rayos X para obtener la estructura cristalina de 2,8 angstroms del dominio P4-P6.
Se realizó un análisis estructural detallado para identificar las interacciones clave y los patrones de plegado.
Se consideró el análisis comparativo con otras estructuras de ARN.

Principales resultados:

El dominio P4-P6 de 160 nucleótidos exhibe una curva aguda, lo que permite que las hélices apiladas se empaquen de manera eficiente.
Dos interacciones críticas de largo alcance estabilizan el dominio: un sacacorchos rico en adenosina coordinado con magnesio y una interacción de bucle de horquilla de pelo GAAA.
Los iones metálicos y las fracciones de ribosa contribuyen a estabilizar el embalaje helicoidal a través de los contactos de la columna vertebral.

Conclusiones:

La estructura determinada revela un extenso empaque de ARN dentro del dominio P4-P6.
Estas interacciones de empaque son cruciales para la función catalítica de las intrones del Grupo I.
Los hallazgos proporcionan información sobre los requisitos estructurales para los ARN funcionales grandes, incluidos el espliceosoma y el ribosoma.

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