Thermoplasma acidophilum proteasome

E. Seemiiller, A. Lupas, D. Stock, J. Lowe, R. Huber, W. Baumeister, Proteasome from Thermoplasma Acidophilum A Threonine Protease , Science 1995, 268, 579-582. 

Akopian, T. N., Kisselev, A. F., and Goldberg, A. L. Processive degradation of proteins and other catatlytic properties of the proteasome from Thermoplasma acidophilum. J. Biol. 

S proteasomes are ubiquitous and essential in eukaryotes (Heinemeyer 2000) ubiquitous but not essential in archaea (Ruepp et al. 1998) and rare and non-essential in bacteria (Knipfer and Shrader 1997 Ete Mot et al. 1999). Because of ist relative simplicity the proteasome from the archaeon Thermoplasma acidophilum (Dahlmann et al. 1989) has played a pivotal role in resolving the structure and enzymatic mechanism of 20S proteasomes (see for example Hegerl et al. 1991 Grziwa et al. 1991 Piihler et al. 1992 Zwickl et al. 1992 Jap et al. 1993). 

The structure of the 20S proteasome (fig. 2.16) from Thermoplasma acidophilum displays four rings stacked upon each other surroimding a central cavity in which pro-... 

While chaperonins assist proteins to fold correctly proteasomes destroy unfolded chains by partial hydrolysis, cutting the chains into a random assortment of pieces from 3 to 30 residues in length with an average length of 8 residues/ Proteasomes destroy not only unfolded and improperly folded proteins but also proteins marked for destruction by the ubiquitin system described in Box 10-C. It has been hard to locate true proteosomes in most bacteria. However, they do contain protease particles with similar characteristics2-1 and archaeons, such as Thermoplasma acidophilum, have proteasomes similar to those of eukaryotes.cc... 

The structure of the 20S proteasome (Fig. 2.13) from Thermoplasma acidophilum displays four rings stacked upon each other surrounding a central cavity in which proteolysis takes place. An N-terminal threonine has been identified as an essential active site residue of the protease center. The OH-group of the threonine functions as a nucleophile during hydrolysis of the petide bond. A similar mechanism of hydrolysis has been shown for other hydrolases, which, because of this property, are now included in the family of N-terminal nucleophile hydrolases. For some /1-subunits of eucaryotes the N-terminal threonine is generated by autoproteolysis of an N-terminal prosequence. 

The 20S proteasome from Thermoplasma acidophilum was the first supramolecular system for which complete assignments of methyl peaks were obtained, and a series... 

---