Subtypes of 20S proteasomes from skeletal muscle.
20S proteasomes from tissues and cells are a mixture of several subtypes. From rat skeletal muscle we have tentatively separated six different subtypes of 20S proteasomes purified from rat skeletal muscle by high-resolution anion exchange chromatography. Immunoblot analysis using antibodies to the beta-subunits LMP2, LMP7 and their constitutive counterparts delta and MB1 revealed that two of the three major subtypes (subtypes I and II) are constitutive proteasomes, whereas two of the three minor subtypes belong to the subpopulation of immuno-proteasomes. Subtype III and IV are intermediate-type proteasomes. Enzymological characterisation of the six subtypes revealed clearly different V(max) values for hydrolysis of fluorogenic peptide substrates as well as significantly different activities measured with a 25-mer polypeptide of the murine cytomegalovirus IE pp89 protein as substrate. Our data show that the properties of 20S proteasomes isolated from a given tissue or cells are always the average of the properties of the whole set of proteasome subtypes.
Dahlmann
B
B
Institut für Biochemie/Charité, Humboldt-Universität Berlin, Monbijoustr. 2, 10117, Berlin, Germany. Burkhardt.Dahlmann@charite.de
Ruppert
T
T
Kloetzel
P M
PM
Kuehn
L
L
D000818:Animals; D015153:Blotting, Western / Q000379:methods; D002845:Chromatography / Q000379:methods; D003546:Cysteine Endopeptidases / Q000145:classification* / Q000302:isolation & purification / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D004789:Enzyme Activation; D007700:Kinetics; D009097:Multienzyme Complexes / Q000145:classification* / Q000302:isolation & purification / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000201:enzymology*; D010447:Peptide Hydrolases / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex; D021122:Protein Subunits; D051381:Rats
D009097:Multienzyme Complexes; D021122:Protein Subunits; D010447:Peptide Hydrolases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex