Purification and properties of the 26S proteasome from the rat brain: evidence for its degradation of myelin basic protein in a ubiquitin-dependent manner.
A ubiquitin(Ub)/ATP-dependent proteolytic complex (26S proteasome) was highly purified from the rat brain. The brain 26S proteasome consisted of 22-110 kDa subunits characteristic of the typical 26S proteasome on the basis of SDS-PAGE. The two-dimensional PAGE (NEPHGE and SDS-PAGE) pattern revealed that the pI values and molecular masses of the brain 26S proteasome subunits were similar to those of the subunits of 26S proteasomes purified from the rat liver and skeletal muscles. The enzymatic properties of the brain 26S proteasome were similar to those of the liver complex and also to the Ub-conjugate degrading activity in the cerebral cortex extract. Furthermore, it was found that the brain 26S proteasome was capable of degrading the myelin basic protein in a Ub-dependent manner. These results indicate that the brain contains the Ub-conjugate-degrading 26S proteasome, the subunit composition of which appears similar to those of the other tissues, and that the myelin basic protein may be a candidate physiological substrate for the brain 26S proteasome.
Akaishi
T
T
Department of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
Shiomi
T
T
Sawada
H
H
Yokosawa
H
H
D000818:Animals; D001923:Brain Chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D004676:Myelin Basic Protein / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000187:drug effects / Q000302:isolation & purification* / Q000378:metabolism*; D011480:Protease Inhibitors / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex; D051381:Rats; D013379:Substrate Specificity; D014452:Ubiquitins / Q000502:physiology*
D004676:Myelin Basic Protein; D011480:Protease Inhibitors; D014452:Ubiquitins; D010447:Peptide Hydrolases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease