A ubiquitin C-terminal isopeptidase that acts on polyubiquitin chains. Role in protein degradation.

摘要: Abstract In the ubiquitin (Ub) pathway, proteins are ligated with polyUb chains and then degraded by a 26 S protease complex. We describe an enzyme, called isopeptidase T, that acts on chains. It is monomeric Ub-binding protein abundant in erythrocytes reticulocytes. The activity of inhibited iodoacetamide Ub aldehyde. Treatment enzyme aldehyde increased its affinity for free Ub, indicating existence two different sites cooperativity between sites. Isopeptidase T polyUb-protein conjugates, but not conjugates which formation was prevented use reductively methylated or abnormal formed mutant contains Lys----Arg substitution at residue 48. converts high molecular mass to lower forms release substrate. Ub-protein conjugate products resistant further action enzyme. stimulates degradation system reconstituted from purified components. also Preincubation did much increase their susceptibility proteolysis On other hand, preincubation complex ATP upon incubation isopeptidase. thus seems role this breakdown remove chain remnants following substrate moiety