Protéines chaperons.

Abstract

La découverte de la fonction chaperon ne date que de dix ans : les chaperons moléculaires facilitent le repliement des protéines et permettent leur désagrégation. La mécanique moléculaire des principaux chaperons bactériens intervenant dans le repliement des protéines a été décryptée. La fonction chaperon ne se limite cependant pas à ces cas bien connus. Il existe aussi de très nombreuses protéines ayant une fonction de chaperon plus spécialisée – qui s’ajoute souvent à une autre fonction. Le rôle « intégratif » des protéines chaperons dans la vie cellulaire normale ou pathologique constitue l’objectif des recherches futures.

The chaperone function was only discovered ten years ago. Chaperones assist protein folding and participate in protein deaggregation. The mechanism of action of the main chaperones involved in protein folding in bacteria is now well understood. HSP70 and HSP40 (DnaK and DnaJ) bind to the nascent polypeptide chains whereas the chaperonin GroEL-GroES functions as a two-stroke motor to extract partially-folded proteins from dead-ends and to provide them an hydrophilic 'Anfinsen cage' where to fold quietly. The function of the chaperones in the different compartments of an eukaryotic cell is less well understood. Many other chaperones have been characterized, prokaryotes and in eukaryotes, which have a more limited number of targets. Many other proteins have a chaperone function, in addition to another function such as a protease activity. The list of chaperones is far from being closed. Chaperones might also participate by their pleiotropic action to the 'buffering' of mutations. The role of chaperones in molecular pathologies and the possibility to manipulate them is now under extensive study.