Résumé
Intracellular proteolysis is an essential cell function. in addition to the elimination of abnormal or excess proteins, it is involved in the control of major cell processes such as division, differentiation, apoptosis, the response to numerous external stimuli and the production of antigenic peptides. In eucaryotes, the ubiquitin/proteasome pathway plays a ma the destruction of intracellular proteins and functions in two steps. First, substrates are marked by covalent attachment of chains of a small protein, ubiquitin, owing to a complex cascade of enzymes. Some of these enzymes are heteromultimeric complexes sharing common functional modules. In a second step, ubiquitinated proteins are recognized and degraded by the 26S proteasome which constitute the proteolytic machinery of the system. This review describes the components of this pathway as well as the mechanisms underlying its extraordinary efficiency and selectivity in the light of the most recent discoveries.