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Incorporation of major histocompatibility complex - encoded subunits LMP2 and LMP7 changes the quality of the 20S proteasome polypeptide processing products independent of interferon-gamma

Item Type:Article
Title:Incorporation of major histocompatibility complex - encoded subunits LMP2 and LMP7 changes the quality of the 20S proteasome polypeptide processing products independent of interferon-gamma
Creators Name:Kuckelkorn, U. and Frentzel, S. and Kraft, R. and Kostka, S. and Groettrup, M. and Kloetzel, P.M.
Abstract:The 20S proteasome is the enzyme complex responsible for the processing of antigens bound by major histocompatibility complex class I molecules. The role of the interferon-gamma (IFN-gamma)-inducible proteasome subunits LMP2 and LMP7 in this process is, however, still controversial. We have studied the effects of IFN-gamma-independent LMP incorporation on the quality of peptides processed from the murine cytomegalovirus IE pp89 25-mer polypeptide substrate through dual cleavages by 20S proteasomes. The incorporation of a single LMP subunit or both LMP2 and LMP7 induces changes in 20S proteasome subunit stoichiometry, alters its cleavage site preference and in consequence, the quality of the generated peptides. When the several hydrolytic activities are tested with short fluorogenic peptide substrates, the Vmax, S0.5 (Km), or both values of 20S proteasomes are altered, depending on the combination of LMP. There exists, however, no obvious correlation between the observed changes in hydrolytic activities against short fluorogenic peptides and the changes in dual cleavage site usage within the 25-mer polypeptide substrate. As judged from the calculated Hill coefficients, the presence of both LMP subunits induces a drastic increase in positive cooperativity between the proteasome subunits.
Keywords:Amino Acid Sequence, B-Lymphocytes, Cysteine Endopeptidases, Cytomegalovirus, Histocompatibility Antigens Class I, Interferon-gamma, Molecular Sequence Data, Multienzyme Complexes, Peptide Biosynthesis, Proteasome Endopeptidase Complex, Proteins, Substrate Specificity, Cultured Tumor Cells, Animals, Mice
Source:European Journal of Immunology
ISSN:0014-2980
Publisher:Wiley (U.S.A.)
Volume:25
Number:9
Page Range:2605-2611
Date:1 September 1995
Official Publication:https://doi.org/10.1002/eji.1830250930
PubMed:View item in PubMed

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