A monoclonal antibody that distinguishes latent and active forms of the proteasome (multicatalytic proteinase complex).
Monoclonal antibodies (mAbs) were generated to proteasome purified from human erythrocytes. Five of six proteasome-specific mAbs reacted with three subunits in the molecular mass range of 25-28 kDa, indicating a common epitope. The other mAb (AP5C10) exhibited a more restricted reactivity, recognizing a 32-kDa subunit of the proteasome purified in its latent state. However, when the proteasome is isolated in its active state, AP5C10 reacts with a 28-kDa subunit, evidence for processing of the proteasome subunits during purification. Purified proteasome preparations which exhibited partial latency have both AP5C10 reactive subunits. Although the 32-kDa subunit appears required for latency, loss of this component and generation of the 28-kDa component are not obligatory for activation. The 32- and 28-kDa subunits can each be further resolved into three components by isoelectric focusing. The apparent loss of 4 kDa during the conversion of the 32- to 28-kDa subunit is accompanied by a shift to a more basic pI for each polypeptide. Western blots of the early steps of proteasome purification reveal an AP5C10-reactive protein at 41 kDa. This protein was separated from proteasomes by sizing chromatography and may represent a pool of precursor subunits. Since the 32-kDa subunit appears necessary for latency, it is speculated to play a regulatory role in ATP-dependent proteolytic activity.
Weitman
D
D
Department of Cell Biology and Anatomy, New York Medical College, Valhalla 10595.
Etlinger
J D
JD
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000911:Antibodies, Monoclonal; D015153:Blotting, Western; D003546:Cysteine Endopeptidases / Q000276:immunology / Q000378:metabolism*; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D009097:Multienzyme Complexes / Q000276:immunology / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D011863:Radioimmunoassay
D000911:Antibodies, Monoclonal; D009097:Multienzyme Complexes; D000255:Adenosine Triphosphate; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex