ATP-dependent proteolysis

In the initial experiments, we resolved reticulocyte lysates on DEAE-cellulose into two crude fractions Fraction 1, which contained proteins not adsorbed to the resin, and Fraction 2, which contained all proteins adsorbed to the resin and eluted with high salt. The original aim of this fractionation was to get rid of hemoglobin, which was known to be in Fraction 1, while most non-hemoglobin proteins of reticulocytes were known to be in Fraction 2. We found that neither fraction was active by itself, but ATP-dependent protein degradation could be reconstituted by combination of the two fractions [13]. The active component in Fraction 1 was a small, heat-stable protein we have exploited its stability to heat treatment for its purification to near homogeneity. We termed this protein at that time APF-1, for ATP-dependent Proteolysis Factor 1 [13]. The identity of APF-1 with ubiquitin was established later by Wilkinson et al. [14], subsequent to the discovery in my laboratory of its covalent ligation to protein substrates, as described below. 

I. A. Proposed role of ATP in protein breakdown conjugation of proteins with multiple chains of the polypeptide of ATP-dependent proteolysis. 

Tanahashi, N. et al. Hybrid proteasomes. Induction by interferon-gamma and contribution to ATP-dependent proteolysis. J. Biol. Chem. 2000, 275, 14336-14345. 

Over the years, a key theme in ATP-dependent proteolysis has been the issue of symmetry-matched vs. symmetry-mismatched complexes. In the light of the... 

J. M. The structure of ClpP at 2.3 A resolution suggests a model for ATP-dependent proteolysis. Cell 1997, 93, 447-456. 

Hershko, A., Ciechanover, A., Heller, H., Haas, A. L. and Rose, 1. A. (1980). Proposed role of ATP in protein breakdown Conjugation of proteins with multiple chains of the polypeptide of ATP-dependent proteolysis. Proc.Natl. Acad. Sci. USA 77, 1783-1786. 

It can be observed that with time the proteasome can be damaged or inactivated by oxidants [62]. Furthermore, the subunit composition of the proteasome changes with age. Alterations for LMP2, LMP7, subunit Z, Ub Thiolesterase and 26 S components have been found [63-66]. Mitochondrial mutations accumulating with aging [67] often decrease ATP production. This also affects the ATP-dependent proteolysis process. 

In both bacterial and eukaryotic cells, cleavage of the peptide bond requires the hydrolysis of ATP. In E. coli, 7080% of all ATP-dependent proteolysis is performed by two protease systems, the Lon protease and the Clp A/P protease. The Lon protease is composed of four identical subunits, whereas the Clp A/P protease is a regulated complex made up of the catalytic Clp C subunit and the ATP-dependent Clp A regulatory subunit. Signals that control the Lon and Clp A/C activities are not well understood, but one contribution may be the presence of certain NH2-terminal amino acids, which... 

Recently, it has been shown that proteasomes, the proteolytic machinery of the ubiquitin/ATP-dependent proteolysis pathway, can also be considered a target of vinblastine. Proteasomes have a crucial role in the regulation of the cell cycle, and proteasome inhibitors can block cell cycle progression and induce apoptosis in certain cell lines. Vinblastine seems to have an inhibitory effect on proteasomes and could thus interfee with mitosis also through this path [165]. 

Ubiquitin, ATP-dependent proteolysis factor 1, APF-J a small polypeptide, 8,500, first isolated during the purification of polypeptide hormones from thymus. U. was subsequently found (by radioimmunoassay) in vertebrates, invertebrates, plants and yeasts. Earlier reports that it induces difierentiation of thymocytes and stimulates adenylate cyclase have not been confirmed the name, ubiquitous immuno-poietic polypeptide (UBIP) is therefore inappropriate. The primary structure of U. is almost identical in insects, trout, cattle and humans. 

The ubiquitin—proteasome system catalyses ATP-dependent proteolysis. It is important in both protein turnover and antigen processing. 

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