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20S proteasome from LMP7 knock out mice reveals altered proteolytic activities and cleavage site preferences
R Stohwasser1, U Kuckelkorn, R Kraft
1Institut für Biochemie der Charité, Humboldt Universität, Berlin, Germany.
FEBS Letters
|March 25, 1996
Abstract:
20S proteasomes of tissues from LMP7 knock out mice which show reduced MHC class I restricted antigen presentation were analyzed with regard to their subunit composition, peptide hydrolyzing activity and their ability to cleave a synthetic 25-mer polypeptide. LMP7 deficiency results in an enhanced incorporation of subunit MB1 and in a 2-3.8-fold increase in Vmax for the Suc-LLVY-MCA hydrolyzing activity. Since LMP7 deficiency also affects the cleavage site preference of 20S proteasomes the reduced MHC class I antigen presentation of LMP7 knock out mice is most likely due to an impairment in peptide generation.