The first characterization of a eubacterial proteasome: the 20S complex of Rhodococcus.
BACKGROUND
The 26S proteasome is the central protease of the ubiquitin-dependent pathway of protein degradation. The proteolytic core of the complex is formed by the 20S proteasome, a cylinder-shaped particle that in archaebacteria contains two different subunits (alpha and beta) and in eukaryotes contains fourteen different subunits (seven of the alpha-type and seven of the beta-type).


RESULTS
We have purified a 20S proteasome complex from the nocardioform actinomycete Rhodococcus sp. strain NI86/21. The complex has an apparent relative molecular mass of 690 kD, and efficiently degrades the chymotryptic substrate Suc-Leu-Leu-Val-Tyr-AMC in the presence or absence of 0.05% SDS. Purified preparations reveal the existence of four subunits, two of the alpha-type and two of the beta-type, the genes for which we have cloned and sequenced. Electron micrographs show that the complex has the four-ringed, cylinder-shaped appearance typical of proteasomes.


CONCLUSIONS
The recent description of the first eubacterial ubiquitin, and our discovery of a eubacterial proteasome show that the ubiquitin pathway of protein degradation is ancestral and common to all forms of life.
Tamura
T
T
Max-Planck-Institute for Biochemistry, Martinsried, Germany.
Nagy
I
I
Lupas
A
A
Lottspeich
F
F
Cejka
Z
Z
Schoofs
G
G
Tanaka
K
K
De Mot
R
R
Baumeister
W
W
D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism / Q000648:ultrastructure; D006801:Humans; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism / Q000648:ultrastructure; D009876:Operon; D010802:Phylogeny; D046988:Proteasome Endopeptidase Complex; D011487:Protein Conformation; D012240:Rhodococcus / Q000145:classification / Q000201:enzymology*; D017386:Sequence Homology, Amino Acid
D009097:Multienzyme Complexes; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex