A novel "active" form of proteasomes from Xenopus laevis ovary cytosol.
The cytosol fraction prepared from Xenopus laevis ovaries by one-step ultracentrifugation catalyzed the hydrolysis of succinyl-leucyl-leucyl-valyl-tyrosine-4-methylcoumaryl-7-amide with or without SDS, an activator of 20S latent proteasomes. Both activities were lost on immunodepletion with antibodies against 20S proteasome. Storage of the cytosol at 4 degrees C led to abolition of the SDS-independent activity, but not the SDS-dependent activity. Upon DEAE-cellulose chromatography, the enzyme catalyzing the SDS-independent activity could be separated from that responsible for the SDS-dependent activity. These results indicate that the ovary cytosol contains a large proportion of a novel, "active" form of proteasomes which does not require SDS but is unstable and is readily converted to a latent form which requires SDS. ATP is known to stabilize 26S protease complex, but ATP reduced SDS-independent activity. It seems that the "active" form of proteasomes (molecular weight: about 1000-kDa) is different from 26S protease complex.
Tokumoto
T
T
Department of Biology, Faculty of Science, Shizuoka University, Japan.
Ishikawa
K
K
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D002848:Chromatography, DEAE-Cellulose; D002850:Chromatography, Gel; D003546:Cysteine Endopeptidases / Q000302:isolation & purification / Q000378:metabolism*; D003600:Cytosol / Q000201:enzymology; D004795:Enzyme Stability; D005260:Female; D007074:Immunoglobulin G / Q000494:pharmacology; D007700:Kinetics; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000302:isolation & purification / Q000378:metabolism*; D010053:Ovary / Q000201:enzymology*; D046988:Proteasome Endopeptidase Complex; D013379:Substrate Specificity; D013997:Time Factors; D014982:Xenopus laevis
D007074:Immunoglobulin G; D009097:Multienzyme Complexes; D000255:Adenosine Triphosphate; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex