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Las glutaredoxinas de monotiol funcionan almacenando y transportando grupos de [Fe2S2] ensamblados en las proteínas
Priyanka Shakamuri1, Bo Zhang, Michael K Johnson
1Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602, USA.
Journal of the American Chemical Society
|September 12, 2012
Resumen
Las chaperonas moleculares HscA y HscB aceleran significativamente la transferencia de clúster de hierro-azufre de IscU a Grx5, esencial para el ensamblaje de clúster de hierro-azufre bacteriano. Esto pone de relieve la necesidad de estos co-caperones para estudios in vitro eficientes.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Biología Molecular Biología Molecular
- Microbiología Microbiología.
Sus antecedentes:
- Los grupos de hierro-azufre (Fe-S) son cofactores vitales para numerosas proteínas.
- La maquinaria de ensamblaje del clúster de hierro-azufre (ISC) en las bacterias involucra proteínas de andamio como IscU y co-chaperones moleculares HscA y HscB.
- IscU sirve como un andamio primario para el ensamblaje de racimos de Fe-S, con HscA y HscB facilitando la transferencia de racimos dependientes de ATP.
Objetivo del estudio:
- Investigar el papel de las co-chaperonas moleculares HscA y HscB en la transferencia de racimos de Fe-S de IscU a apo-Grx5.5.
- Para cuantificar la mejora de la tasa de transferencia de clúster de Fe-S mediada por HscA/HscB/Mg-ATP.
Principales métodos:
- Utilizó espectroscopia de dicroísmo circular (CD) para monitorear la transferencia de racimos de [Fe(2) S(2) ](2+).
- Se compararon las tasas de transferencia de clúster de IscU ligado a [Fe(2) S(2) ](2+) a apo-Grx5 en ausencia y presencia de HscA/HscB/Mg-ATP.
- Determinó la constante de tasa de segundo orden para el proceso de transferencia.
Principales resultados:
- Se observó una mejora de 700 veces en la tasa de transferencia de clúster [Fe(2) S(2) ](2+) en presencia de HscA/HscB/Mg-ATP.
- Calculó una constante de velocidad de segundo orden de 20.000 M−1 min−1 a 23 °C para la transferencia mediada por HscA/HscB.
- Se ha demostrado que HscA y HscB son indispensables para una transferencia eficiente de clusters [Fe(2) S(2) ](2+) dependientes de ATP desde IscU a Grx5.
Conclusiones:
- HscA y HscB son esenciales para la transferencia eficiente de clusters [Fe(2) S(2) ](2+) dependientes de ATP desde IscU a Grx5.
- Las glutaredoxinas de monotiol (Grx's) probablemente juegan un papel en el almacenamiento y el transporte de grupos de Fe-S ensamblados en IscU.
- Los estudios in vitro de la transferencia de clúster [Fe(2) S(2) ](2+) -IscU requieren la inclusión del sistema de co-chaperón HscA/HscB para una interpretación precisa.
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