Molecular Interaction of the Proteasome (multicatalytic Proteinase). Evidence That the Proteasome is Not a Constituent of the '26 S' Multienzyme Complex
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On the basis of recent reports that suggested that proteasomes, via an ATP-dependent process, become integral components of a '26 S' complex possessing 3-carboxypropionyl-Leu-Leu-Val-Tyr 4-methylcoumarin-7-ylamide-hydrolysing activity, we have investigated the molecular interaction of proteasomes in ATP-stabilized fraction II (proteins absorbed on DEAE-matrix and eluted with 0.5 M-KCl) of rabbit reticulocytes and mouse liver. Analysis of the various extracts by (NH4)2SO4 fractionation, velocity-gradient centrifugation, non-denaturing PAGE and SDS/PAGE and immunoblotting with proteasome-specific antisera failed to identify the proteasome as part of a higher-molecular-mass '26 S' multienzyme complex. In all instances proteasomes are identified in their 'free' 650 kDa '20 S' form. In addition to the proteasome and independent of the presence of MgATP, we isolated a high-molecular-mass proteinase whose electrophoretic migration behaviour and sedimentation rate correspond to that of the previously described '26 S' proteinase. This '26 S' proteinase possesses a strong 3-carboxypropionyl-Leu-Leu-Val-Tyr 4-methylcoumarin-7-ylamide-hydrolysing activity and is composed of several non-identical polypeptides in the molecular-mass range 20-150 kDa. Despite its similarity to proteasomal enzyme activity, protein analysis and immunoblotting experiments demonstrate that neither the intact proteasome nor subunits thereof are components of the '26 S' proteinase complex.
Amsterdam A, Pitzer F, Baumeister W Proc Natl Acad Sci U S A. 1993; 90(1):99-103.
PMID: 8380501 PMC: 45607. DOI: 10.1073/pnas.90.1.99.
Boes B, Hengel H, Ruppert T, Multhaup G, Koszinowski U, Kloetzel P J Exp Med. 1994; 179(3):901-9.
PMID: 8113682 PMC: 2191397. DOI: 10.1084/jem.179.3.901.
Families of serine peptidases.
Rawlings N, Barrett A Methods Enzymol. 1994; 244:19-61.
PMID: 7845208 PMC: 7133253. DOI: 10.1016/0076-6879(94)44004-2.
Proteasomes: multicatalytic proteinase complexes.
Rivett A Biochem J. 1993; 291 ( Pt 1):1-10.
PMID: 7682410 PMC: 1132471. DOI: 10.1042/bj2910001.
Studies on the activation by ATP of the 26 S proteasome complex from rat skeletal muscle.
Dahlmann B, Kuehn L, Reinauer H Biochem J. 1995; 309 ( Pt 1):195-202.
PMID: 7619056 PMC: 1135819. DOI: 10.1042/bj3090195.