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Functional Characterization of RING-Type E3 Ubiquitin Ligases In Vitro and In Planta
Published on: December 5, 2019
Una ligasa de ubiquitina transfiere cadenas de poliubiquitina preformadas de una enzima conjugadora a un sustrato
Wei Li1, Daqi Tu, Axel T Brunger
1Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
Nature
|February 21, 2007
Resumen
Los investigadores exploraron la formación de la cadena de ubiquitina para la degradación de las proteínas. Descubrieron que las cadenas de ubiquitina están preensambladas en una enzima (E2) antes de unirse a sustratos, un hallazgo novedoso para el sistema ubiquitina-proteasoma.
Área de la Ciencia:
- Biología celular Biología celular.
- La bioquímica es la bioquímica.
- Biología Molecular Biología Molecular
Sus antecedentes:
- Las células eucariotas degradan las proteínas de corta duración a través del proteosoma, un proceso que implica ubiquitinación.
- La ubiquitinación requiere enzimas E1, E2 y E3, con las ligasas E3 (dominio HECT o RING) que catalizan la poliubiquitinación.
- El mecanismo preciso de la catálisis de la ligasa E3 en la poliubiquitinación sigue siendo poco conocido.
Objetivo del estudio:
- Para dilucidar el mecanismo de la poliubiquitinación mediada por E3 ligasa.
- Investigar las funciones de Ube2g2 (E2) y gp78 (E3) en la vía de degradación asociada al retículo endoplasmático.
Principales métodos:
- La expresión recombinante del ratón Ube2g2 y el gp78 humano en Escherichia coli.
- Ensayos bioquímicos para analizar las reacciones de poliubiquitinación.
- Caracterización de los mecanismos de preensamblaje y transferencia de la cadena de ubiquitina.
Principales resultados:
- La demostrada poliubiquitinación mediada por Ube2g2/gp78 implica el preensamblaje de las cadenas de ubiquitina vinculadas a Lys 48 en la cisteína catalítica de Ube2g2.
- Se identificó una reacción de transferencia basada en la aminólisis entre dos moléculas de Ube2g2 para el alargamiento de la cadena de ubiquitina.
- Se demostró que las cadenas de ubiquitina preensambladas pueden transferirse de Ube2g2 a un substrato residuo de lisina.
Conclusiones:
- El sistema Ube2g2/gp78 utiliza un nuevo mecanismo para la poliubiquitinación que involucra cadenas de ubiquitina preensambladas.
- Este hallazgo proporciona nuevos conocimientos sobre el mecanismo catalítico de las ligasas de ubiquitina E3.
- Comprender este proceso es crucial para la degradación de las proteínas mal plegadas en el retículo endoplasmático.
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