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Evidencia de una modificación post-traducional, el aspartil aldehído, en una proteína de membrana fotosintética
Lorraine B Anderson1, Anthony J A Ouellette, Julian Eaton-Rye
1Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, St. Paul, Minnesota 55108, USA.
Journal of the American Chemical Society
|July 9, 2004
Resumen
Los investigadores identificaron un nuevo aminoácido modificado en el fotosistema II (PSII). Este descubrimiento arroja luz sobre los residuos que contienen carbonilo cruciales para la función de este complejo de proteínas fotosintéticas esenciales.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- La investigación de la fotosíntesis en la investigación de la fotosíntesis.
- La Proteómica es la Proteómica.
Sus antecedentes:
- La fotosíntesis oxigenada se basa en el fotosistema II (PSII) para la oxidación del agua y la reducción de la plastoquinona.
- Tres subunidades de PSII poseen grupos reactivos que se unen a aminas y fenilhidrazina, lo que sugiere modificaciones que contienen carbonilo.
- Se supone que estas modificaciones implican alteraciones co- o post-traduccionales de los aminoácidos.
Objetivo del estudio:
- Para identificar residuos específicos de aminoácidos modificados dentro de la subunidad CP47 del fotosistema II.
- Para investigar la naturaleza de los grupos reactivos que contienen carbonilo en las subunidades PSII.
Principales métodos:
- Se empleó espectrometría de masas en tándem para analizar la subunidad CP47.
- Los residuos modificados fueron etiquetados por afinidad utilizando biotina-LC-hidrazida o biocitina hidrazida, que específicamente etiquetan grupos carboniles.
- La purificación de afinidad seguida de espectrometría de masas en tándem identificó péptidos etiquetados con hidrazida.
Principales resultados:
- Se identificó un péptido etiquetado con hidrazida con la secuencia XKEGR.
- El mapeo cuantitativo de péptidos y el etiquetado de metilamina apoyaron estos hallazgos.
- La secuencia genética y los datos de espectrometría de masas predicen que "X" es un residuo de ácido aspártico modificado.
Conclusiones:
- Se propone una nueva modificación del aminoácido, el aldehído de aspartilo, para el ácido aspártico en la posición 348 (D348) en la subunidad CP47.
- Esta modificación probablemente explica los grupos reactivos de carbonilo observados en PSII.
- Los hallazgos contribuyen a comprender las complejidades estructurales y funcionales del fotosistema II.
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