The human 26 S and 20 S proteasomes generate overlapping but different sets of peptide fragments from a model protein substrate.
Intracellular protein degradation is a major source of short antigenic peptides that can be presented on the cell surface in the context of major histocompatibility class I molecules for recognition by cytotoxic T lymphocytes. The capacity of the most important cytosolic protease, the 20 S proteasome, to generate peptide fragments with an average length of 7-8 amino acid residues has been thoroughly investigated. It has been shown that the cleavage products are not randomly generated, but originate from the commitment of the catalytically active subunits to complex recognition motifs in the primary amino acid sequence. The role of the even larger 26 S proteasome is less well defined, however. It has been demonstrated that the 26 S proteasome can bind and degrade ubiquitin-tagged proteins and minigene translation products in vivo and in vitro, but the nature of the degradation products remains elusive. In this study, we present the first analysis of cleavage products from in vitro digestion of the unmodified model substrate beta-casein with both the 26 S and 20 S proteasome. The data we obtained show that 26 S and 20 S proteasomes generate overlapping, but at the same time substantially different, sets of fragments by following very similar instructions.
Emmerich
N P
NP
Department of Immunology, Institute for Cell Biology, University of Tübingen, Auf der Morgenstelle 15, D-72076 Tübingen, Germany.
Nussbaum
A K
AK
Stevanovic
S
S
Priemer
M
M
Toes
R E
RE
Rammensee
H G
HG
Schild
H
H
D000251:Adenosine Triphosphatases / Q000097:blood; D000595:Amino Acid Sequence; D002364:Caseins / Q000737:chemistry* / Q000378:metabolism*; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D003546:Cysteine Endopeptidases / Q000097:blood* / Q000302:isolation & purification; D004591:Electrophoresis, Polyacrylamide Gel; D004912:Erythrocytes / Q000201:enzymology; D006801:Humans; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000097:blood* / Q000302:isolation & purification; D010446:Peptide Fragments / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000097:blood* / Q000302:isolation & purification; D011480:Protease Inhibitors / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex; D014452:Ubiquitins / Q000378:metabolism
D002364:Caseins; D009097:Multienzyme Complexes; D010446:Peptide Fragments; D011480:Protease Inhibitors; D014452:Ubiquitins; D010447:Peptide Hydrolases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease; D000251:Adenosine Triphosphatases