4 - Chaperonin-Mediated Folding and Assembly of Proteins in Mitochondria

Abstract

This chapter focuses on mediated folding and assembly of proteins in mitochondria. Molecular chaperone proteins bind to non-native protein structures, which expose hydrophobic regions that are buried in the interior of a completely folded protein, and thus prevent the aggregation of these structures. Within a cell, these interactive surfaces are exposed during synthesis, when polypeptide chains emerge from ribosomes, and at later stages of the folding pathway. Membrane translocation requires an unfolded, translocation-competent conformation of polypeptide chains. This implies, on one hand, that cytosolic forms of the proteins have to be unfolded on membrane translocation or that folding has to be suppressed until the final location is reached. On the other hand, after membrane translocation has been achieved, folding of organellar proteins into the native conformation must occur. On the basis of these considerations, it can be expected that the biogenesis of organellar proteins strongly depends on molecular chaperone proteins.