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Optimized Negative Staining: a High-throughput Protocol for Examining Small and Asymmetric Protein Structure by Electron Microscopy
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La estructura de una carotenoide oxigenasa que forma la retina
Daniel P Kloer1, Sandra Ruch, Salim Al-Babili
1Institut für Organische Chemie und Biochemie, Albert-Ludwigs-Universität, Albertstrasse 21, 79104 Freiburg im Breisgau, Germany.
Science (New York, N.Y.)
|April 12, 2005
Resumen
Las enzimas que producen retina y apocarotenoides presentan un pliegue de hélice beta único. El análisis de rayos X reveló cómo estas oxigenasas se unen y dividen los carotenoides, alterando su estructura para la acción enzimática.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Biología Estructural Biología estructural.
- Enzimología Enzimología.
Sus antecedentes:
- Las enzimas que sintetizan la retina y los apocarotenoides pertenecen a una familia relacionada.
- Comprender su estructura es clave para dilucidar su función en el metabolismo de los carotenoides.
Objetivo del estudio:
- Determinar la estructura tridimensional de una enzima clave involucrada en la producción de retina y apocarotenoides.
- Para investigar el mecanismo de unión y escisión de carotenoides por esta enzima.
Principales métodos:
- Análisis de difracción de rayos X de una enzima purificada.
- Estudios cristalográficos de la enzima con un derivado carotenoide unido.
Principales resultados:
- La enzima, una oxigenasa, posee un pliegue de hélice beta de siete palas con un centro Fe2+-4-His.
- Un túnel no polar proporciona acceso al sitio activo, alojando un derivado carotenoide.
- La unión de carotenoides induce un cambio conformacional de todo trans a cis-trans-cis, con la escisión final que ocurre en el centro Fe2+.
Conclusiones:
- El análisis estructural proporciona información sobre el mecanismo catalítico de la escisión de carotenoides por esta familia de enzimas.
- Los hallazgos contribuyen a la comprensión de la biosíntesis de la retina y apocarotenoides relacionados.
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