Multicatalytic proteinase complex

Protein modification by the covalent attachment of ubiquitin chains serves as a signal to mark proteins for the degradation by a multicatalytic proteinase complex called the proteasome. Thus the ubiquitin proteasome system (UPS) controls the stability of proteins in a... 

M. Orlowski, The Multicatalytic Proteinase Complex, a Major Extralysomal Proteolytic System , Biochemistry 1990, 29, 10289-10297. 

Cardozo, C., Vinitsky, A., Michaud, C., and Orlowski, M. Evidence that the nature of amino acid residues in the P3 position directs substrates to distinct catalytic sites of the pituitary multicatalytic proteinase complex (proteasome). Biochemistry 1994,... 

PI. Pacifici, R. E., Kono, Y., and Davies, K. J., Hydrophobicity as the signal for selective degradation of hydroxyl radical-modified hemoglobin by the multicatalytic proteinase complex, proteasome. J. Biol. Chem. 268, 15405—15411 (1993). 

C., Evidence for the presence of five distinct proteolytic components in the pituitary multicatalytic proteinase complex. Properties of two components cleaving bonds on the carboxyl side of branched chain and small neutral amino acids. Biochemistry 1993, 32, 1563-1572. 

C., Orlowski, M., Inhibition of the chy-motrypsin-like activity of the pituitary multicatalytic proteinase complex. Biochemistry 1992, 31, 9421-9428. 

After the discovery of this multicatalytic proteinase complex, which has a sedimentation coefficient of 20 S, it was realised that it was very similar to another particle that had been isolated independently. The latter, known as a prosome, is associated with mRNA that is repressed from translation. Generally a cell has two pools of mRNA, one that is being actively translated and the other that is inhibited from translation. Prosome-like particles have been detected in duck erythroblasts where they inhibit translation of the portion of the mRNA that is bound to the erythroblasts (Akhayat et al, 1967 Nothwang et al, 1992). The multicatalytic proteinase (20S) associates with two factors (CFl and CF2) to form a 26S complex referred to as a proteasome (Fig. 5.4). The proteasome (26S) and the multicatalytic proteinase complex (20S) are thought to participate in ubiquitin-dependent and ubiquitin-independent proteolysis, respectively. 

Rivett, A.J. (1993). Proteasomes multicatalytic proteinase complexes. Biochem. ]., 291, 1-10. 

Multicatalytic Proteinase Complex (MPC) A massive complex of proteolytic enzymes that is found in the cytosol of many eukaryotic cells and seems to fianction in the programmed destruction of cellular proteins. 

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