Isolation and characterization of a novel endogenous inhibitor of the proteasome

Journal Article · Tue Oct 08 00:00:00 EDT 1991 · Biochemistry; (United States)

OSTI ID:5702732

Li, Xiaochong ^[1]; Gu, M; Etlinger, J D ^[2]

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1. New York Medical Coll., Valhalla (United States) State Univ. of New York, Brooklyn (United States)
2. New York Medical Coll., Valhalla (United States)

A novel endogenous inhibitor of the proteasome (high molecular weight multicatalytic protease) has been isolated and characterized from human erythrocytes. After purification by ion-exchange and sizing chromatography, the inhibitor displayed a native molecular mass of approximately 200 kDa and contained a single subunit of 50 kDa with an isoelectric point of 6.9. Although the inhibitor noncompetitively blocks proteolysis of (methyl-{sup 14}C)-{alpha}-casein and inhibits hydrolysis of Suc-Leu-Leu-Val-Tyr-AMC, it did not affect hydrolysis of other peptide substrates, such as MeOSuc-Phe-Leu-Phe-MNA and Z-Ala-Arg-Arg-MNA. To further characterize the 50-kDa inhibitor, a monoclonal antibody (MI-8) was generated that showed specific binding upon Western blot analysis of both native PAGE and SDS-PAGE. Immunoprecipitation with MI-8 specifically removed inhibitor activity against the proteasome. The 50-kDa inhibitor is distinct from a previously described 40-kDa inhibitor of the proteasome on the basis of lack of cross-reactivity with MI-8 and dissimilar peptide digest patterns. It is suggested that these endogenous inhibitors may have a role in ATP/ubiquitin-dependent proteolysis and/or other cellular functions involving this protease.

• OSTI ID: 5702732
• Journal Information: Biochemistry; (United States), Vol. 30:40; ISSN 0006-2960
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
ENZYME INHIBITORS
RADIOIMMUNOASSAY
PEPTIDE HYDROLASES
ENZYME ACTIVITY
CARBON 14 COMPOUNDS
CASEIN
ENZYMATIC HYDROLYSIS
MOLECULAR STRUCTURE
MONOCLONAL ANTIBODIES
ANTIBODIES
BIOASSAY
CARBON COMPOUNDS
CHEMICAL REACTIONS
DECOMPOSITION
DIAGNOSTIC TECHNIQUES
ENZYMES
HYDROLASES
HYDROLYSIS
IMMUNOASSAY
IMMUNOLOGY
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
LYSIS
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
PROTEINS
RADIOASSAY
RADIOIMMUNODETECTION
RADIOIMMUNOLOGY
SOLVOLYSIS
TRACER TECHNIQUES
550200* - Biochemistry