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Perspectivas estructurales sobre los mecanismos moleculares de la catálisis inducida por OsFBN5 de OsSPS3

Han Xiao^1,2, Xing-Xing Shi^1,2, Min Li^1,2

¹State Key Laboratory of Green Pesticide, Central China Normal University, Wuhan, People's Republic of China.

|January 6, 2026

Resumen

La Fibrilina 5 (FBN5) activa la Solanesil difosfato sintasa (SPS) induciendo un cambio conformacional, lo que permite que ambos monómeros de la enzima funcionen. Este descubrimiento aclara la regulación de la biosíntesis de plastoquinona-9 en las plantas.

Área de la Ciencia:

Bioquímica vegetal
Fotosíntesis
Regulación enzimática

Sus antecedentes:

La Solanesil difosfato sintasa (SPS) es vital para la fotosíntesis, produciendo precursores para la plastoquinona-9 (PQ-9).
La Fibrilina 5 (FBN5) mejora la actividad de la SPS, pero su mecanismo regulatorio es desconocido.
OsSPS3 en arroz es una isoforma clave de SPS para la síntesis de PQ-9, y su deficiencia causa fotodaño.

Objetivo del estudio:

Elucidar el mecanismo molecular de la regulación mediada por FBN5 de la actividad de OsSPS3.
Revelar la base estructural del mecanismo catalítico de OsSPS3.
Comprender el papel de FBN5 en la vía de biosíntesis de PQ-9.

Principales métodos:

Cristalografía de rayos X de OsSPS3 (apo y unida a inhibidor).
Criomicroscopía electrónica del complejo OsSPS3-FBN5 (apo y unida a ligando).
Ensayos de actividad enzimática de homodímeros y heterodímeros de OsSPS3 de tipo salvaje y mutantes.

Principales resultados:

Las estructuras cristalinas revelaron un mecanismo catalítico alterno para el dímero OsSPS3.
Las estructuras de criomicroscopía electrónica mostraron que la unión de FBN5 induce un cambio conformacional en OsSPS3, activando ambos monómeros.
FBN5 mejora la actividad de OsSPS3 al promover un mecanismo catalítico síncrono.

Conclusiones:

La unión de OsFBN5 transforma OsSPS3 en un dímero completamente activo a través de un cambio conformacional.
Este estudio proporciona información estructural sobre el mecanismo catalítico dinámico de OsSPS3 y la regulación por FBN5.
La comprensión de esta vía es crucial para mejorar la fotosíntesis y la tolerancia al estrés en las plantas.

Palabras clave:

Solanesil difosfato sintasa Fibrilina 5 Plastoquinona-9 Biosíntesis Fotosíntesis Regulación enzimática Estructura de proteínas Cristalografía de rayos X Criomicroscopía electrónica Arroz

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