Investigadores del Centro Nacional de Biotecnología del Consejo Superior de Investigaciones Científicas (CNB-CSIC) y la Universidad del País Vasco han colaborado en el descubrimiento del mecanismo de funcionamiento de la chaperona DNAJA2, perteneciente a la familia de las llamadas Hsp40 o proteínas J, el más diverso dentro de las chaperonas. El trabajo, publicado en Nature Communications, desvela cómo las diferentes condiciones celulares afectan a su función.
Las chaperonas moleculares son un variado grupo de proteínas involucradas en la síntesis, plegamiento, prevención de la formación de agregados y degradación de las proteínas celulares. Debido a ese papel tan crítico en el control de la calidad de las proteínas, los errores en su funcionamiento están asociados a procesos cancerígenos y a distintas enfermedades degenerativas. Muchas de estas chaperonas pueden funcionar como moléculas individuales (monómeros), o en conjunto, desde dímeros a estructuras oligoméricas, y algunas varían su estado dependiendo de las circunstancias. Este trabajo muestra que la chaperona DNAJA2, de la familia Hsp40 (hasta ahora conocidas como auxiliares de las chaperonas Hsp70, pero cuyo papel se está mostrando cada día más importante), es una de las que puede actuar tanto como monómero como oligómero.
- Las chaperonas moleculares son clave para el equilibrio entre la síntesis y degradación de las proteínas celulares
- Para analizar la función de estos complejos y conocer su estructura, los científicos han empleado el criomicroscopio electrónico del Centro Nacional de Biotecnología del CSIC
Un trabajo codirigido por investigadores del Centro Nacional de Biotecnología del Consejo Superior de Investigaciones Científicas (CSIC) ha determinado el mecanismo de funcionamiento del complejo CCT, una de las chaperonas moleculares más importantes en organismos eucariotas. Los científicos, que publican sus resultados en el último número de la revista Nature Communications, han empleado un criomicroscopio electrónico de última generación.
La flexibilidad de las chaperonas moleculares, un conjunto de proteínas presentes en todas las células, favorece que actúen en diferentes procesos. Por un lado, ayudan a que otras proteínas recién formadas adopten la estructura tridimensional adecuada para su funcionamiento (plegamiento), pero, por otro, contribuyen a su degradación, un proceso opuesto al anterior, pero también esencial a nivel celular.
A study conducted jointly by scientists from the United States and Spain shows how Hsp70 chaperones work. As if they were nanomachines, the Hsp70 generate force on other proteins through collisions and stretching, to break bonds between them or transport them through the membranes of different cell compartments.
Según se van sintetizando las proteínas en los ribosomas, éstas tienen que ir tomando la forma adecuada para poder ejercer su función. Aunque las características físico-químicas de los aminoácidos que las forman determinan en gran parte la forma que adquieren, hay muchas proteínas que necesitan ayuda extra de parte de un grupo de proteínas conocidas como chaperonas.
Para comprender mejor cómo funcionan estas proteínas, en su laboratorio del Centro Nacional de Biotecnología del CSIC (CNB), el grupo dirigido por José María Valpuesta ha utilizado la microscopía electrónica. Gracias a esta técnica han podido determinar por primera vez la estructura de un complejo formado por la chaperona DnaJ y su sustrato, lo que les ha permitido observar cómo la chaperona cambia la estructura del sustrato y con ello su función.
En colaboración con la Universidad del País Vasco, el investigador postdoctoral del CNB Jorge Cuéllar ha identificado además en dicha chaperona una zona de gran flexibilidad que le permite adaptarse a la forma de distintas proteínas. Como se puede apreciar en la imagen de abajo, la forma que adopta la chaperona DnaJ (en azul) cambia radicalmente en función del sustrato al que se une (RepE1-144, RepE o Rep54; en amarillo). De este modo, una misma chaperona es capaz de unirse a una variedad de proteínas diferentes, consiguiendo en todas ellas que adquieran la forma necesaria para funcionar.
- Cuéllar J, Perales-Calvo J, Muga A, Valpuesta JM, Moro F. Structural insights into the chaperone activity of the 40 kDa heat shock protein DnaJ. Binding and remodeling of a native substrate. J Biol Chem 2013 Apr 11. [doi: 10.1074/jbc.M112.430595].
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