|
KMID : 0616619990050010039
|
|
Journal of Soonchunhyang Medical College
1999 Volume.5 No. 1 p.39 ~ p.49
|
|
|
Study on the ATPase-activated Proteolysis by the 20S Proteasome from Thermoplasma acidophilum
|
|
Cho Man-Hee
Kim Chang-Se
|
|
|
Abstract
|
|
|
The eukaryotic 26S proteasome is an ATP/ubiquitin-dependent proteolytic complex consisting of the 20S core particle and 19S ATPase complex. However, because of its complexity and unstable properties, this study was carried out to present more simple and stable model for the ATP-activated proteolytic complex in prokaryotes which can take the place of the eukaryotic 26S proteasome. For this purpose, recombinant Thermoplasma 20S proteasome (T20S) and Methanococcus MS4, a sequence homolog of one ATPase subunit in the 19S ATPase complex, were successfully isolated from Escherichia coli (E. coli).
The α and β subunits of T20S expressed in E. coli could assemble for themselves, and showed the peptide-hydrolyzing activity. Whereas both T20S and R20S (the 20S complex from rabbit skeletal muscle) had the highest peptidase activity against Suc-LLVY-AMC, a good substrate for chymotrypsin-like peptidase activity, the specific activity of T20S was slightly lower than that of R20S. In addition, several reagents such as KCI, SDS, and ovalbumin were shown to have different effects on the peptidase activities between T20S and R20S.
When the ATPase activity of the purified MS4 were assayed , the Km for ATP was
about 0.5 mM, and casein could stimulate the activity more than 2 fold without the change in Km. This result implicates that protein-activated ATPase may induce the conformational change of casein, and therefore suggests that MS4 ATPase may activate the proteolytic activity of the 20S proteasome via accelerating the recognition and translocation of the protein substrates.
|
|
|
KEYWORD
|
|
|
|
|
|
FullTexts / Linksout information
|
|
|
|
|
|
Listed journal information
|
|
|
|
|