The Ubiquitin System, an Immense Realm

摘要: Among the functions of intracellular proteolysis are elimination misfolded or otherwise abnormal proteins; maintenance amino acid pools in cells affected by stresses, such as starvation; and generation protein fragments that act hormones, antigens, other effectors. Many proteins either conditionally constitutively short-lived, with vivo half-lives can be brief a few minutes. In some cases, proteolytic pathway targets destroys cotranslationally, i.e., an emerging polypeptide chain degraded while it is still ribosome-associated peptidyl-tRNA (1, 2). The regulated processive degradation carried out largely ubiquitin (Ub)- proteasome system (Ub system), conjunction molecular chaperones, autophagy, lysosomal proteolysis. Other mediators of intracellular include proteases caspases, calpains, separases. These nonprocessive function “upstream” components Ub system, generating targeted to short peptides Ub-mediated pathways. Proteins damaged, misfolded, often recognized selectively destroyed system. Physiologically important exceptions conformationally perturbed and/or their aggregates harmful but cannot efficaciously repaired removed. resulting proteotoxicity underlies both aging specific diseases, including neurodegeneration.