Localization of subunits in proteasomes from <i>Thermoplasma acidophilum</i> by immunoelectron microscopy

Grziwa, Anja; Baumeister, Wolfgang; Dahlmann, Burkhardt; Köpp, F.

doi:10.1016/0014-5793(91)81256-8

Cited by 119 publications

(65 citation statements)

References 9 publications

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“…The overall structure of proteasomes is well conserved during evolution and consists of four stacked rings. As most clearly shown for the proteasome from the archaeon Thermoplasma acidophilum, each of the two end rings consist of seven ␣ subunits while each of the two central rings is composed of seven ␤ subunits (4,5). The active sites are formed by the N-terminal threonine residues of the ␤ subunits, which face a central cavity in the cylindrical particle (6,7).…”

mentioning

confidence: 90%

Subunit arrangement in the human 20S proteasome

Köpp

Hendil

Dahlmann

et al. 1997

Proc. Natl. Acad. Sci. U.S.A.

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108

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In human 20S proteasomes two copies of each of seven different ␣-type and seven different ␤-type subunits are assembled to form a stack of four sevenmembered rings, giving the general structure ␣ 1-7 , ␤ 1-7 , ␤ 1-7 , ␣ 1-7 . By means of immunoelectron microscopy and chemical crosslinking of neighboring subunits, we have determined the positions of the individual subunits in the proteasome. The topography shows that for the trypsin-like, the chymotrypsin-like, and the postglutamyl cleaving activities, the pairs of ␤ type subunits, which are thought to form active sites, are nearest neighbors.

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mentioning

confidence: 90%

Subunit arrangement in the human 20S proteasome

Köpp

Hendil

Dahlmann

et al. 1997

Proc. Natl. Acad. Sci. U.S.A.

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108

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“…MCP has a native molecular weight of ~ 700 kDa, and in eukaryotes it is composed of at least 14 distinct subunits with molecular masses between 21 and 32 kDa [4]. The subunits are arranged in four rings each containing 7 subunits; the rings stack upon one another to form a cylindrical structure [5]. The multicatalytic protease exhibits at least five endopeptidase activities that cleave bonds at the carboxyl side of basic, hydrophobic-neutral and acidic amino acids [6].…”

Section: Introductionmentioning

confidence: 99%

Human lymphoblast and erythrocyte multicatalytic proteases: differential peptidase activities and responses to the 11S regulator

et al. 1995

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The multicatalytic protease (MCP) or 20S proteasome was purified from human red blood cells and two lymphoblastoid cell lines, 721.45 which constitutively expresses protease subunits LMP2 and LMP7, and 721.174 in which genes for these subunits are deleted. Each MCP was assayed using a series of fluorogenic peptides. The hydrophobic peptides gGGF-MCA, sRPFHLLVY-MCA and sLY-MCA were particularly good substrates for 721.45 MCP as compared to the enzyme from 721.174 and red blood cells. In addition, hydrolysis of gGGF-MCA and sLY-MCA was activated by human red blood cell and recombinant regulators to a greater extent using MCP from 721.45 lymphoblasts. Thus, LMP2/LMP7 and regulator appear to act synergistically in the enhanced degradation of gGGF-MCA and sLY-MCA by the multicatalytic protease.

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“…The 20 S proteasome is a 700-kDa particle with multiple peptidase activities, including a chymotryptic-, tryptic-, and peptidylglutamyl-like activity (4 -6). It is a cylindrical-shaped structure composed of four rings, the outer two each contain seven ␣-subunits and the inner two each contain seven ␤-subunits (7,8). Proteolysis occurs in the central chamber of this particle and is catalyzed through a nucleophilic attack on the peptide bond by the N-terminal threonine hydroxyl groups on certain ␤-subunits, named X (⑀), Y(␦), Z (HCO), and their homologues LMP2, LMP7, and LMP10 (MECL-1) (9 -12).…”

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confidence: 99%

Lactacystin and clasto-Lactacystin β-Lactone Modify Multiple Proteasome β-Subunits and Inhibit Intracellular Protein Degradation and Major Histocompatibility Complex Class I Antigen Presentation

Craiu

Gaczyńska

Akopian

et al. 1997

Journal of Biological Chemistry

367

268

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The antibiotic lactacystin was reported to covalently modify ␤-subunit X of the mammalian 20 S proteasome and inhibit several of its peptidase activities. However, we demonstrate that [ 3 H]lactacystin treatment modifies all the proteasome's catalytic ␤-subunits. Lactacystin and its more potent derivative ␤-lactone irreversibly inhibit protein breakdown and the chymotryptic, tryptic, and peptidylglutamyl activities of purified 20 S and 26 S particles, although at different rates. Exposure to these agents for 1 to 2 h reduced the degradation of short-and long-lived proteins in four different mammalian cell lines. Unlike peptide aldehyde inhibitors, lactacystin and the ␤-lactone do not inhibit lysosomal degradation of an endocytosed protein. These agents block class I antigen presentation of a model protein, ovalbumin (synthesized endogenously or loaded exogenously), but do not affect presentation of the peptide epitope SIINFEKL, which does not require proteolysis for presentation. Generation of most peptides required for formation of stable class I heterodimers is also inhibited. Because these agents inhibited protein breakdown and antigen presentation similarly in interferon-␥-treated cells (where proteasomes contain LMP2 and LMP7 subunits in place of X and Y), all ␤-subunits must be affected similarly. These findings confirm our prior conclusions that proteasomes catalyze the bulk of protein breakdown in mammalian cells and generate the majority of class I-bound epitopes for immune recognition.

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Localization of subunits in proteasomes from Thermoplasma acidophilum by immunoelectron microscopy

Cited by 119 publications

References 9 publications

Subunit arrangement in the human 20S proteasome

Subunit arrangement in the human 20S proteasome

Human lymphoblast and erythrocyte multicatalytic proteases: differential peptidase activities and responses to the 11S regulator

Lactacystin and clasto-Lactacystin β-Lactone Modify Multiple Proteasome β-Subunits and Inhibit Intracellular Protein Degradation and Major Histocompatibility Complex Class I Antigen Presentation

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