20 S proteasomes are assembled via distinct precursor complexes. Processing of LMP2 and LMP7 proproteins takes place in 13-16 S preproteasome complexes.
The non-essential mouse proteasome beta-type subunits LMP2 and LMP7 are thought to connect proteasomes to the MHC class I antigen processing pathway. Both subunits are synthesized as proproteins. We have studied the processing of both subunits, correlated with the maturation of 20 S proteasomes in mouse T cells. Our data show that proteasome assembly occurs via 13-16 S precursor complexes which possess a protein pattern distinct from that of 20 S proteasomes. Both LMP2 and LMP7 proproteins are processed within these preproteasome complexes and only their processed forms become part of active 20 S proteasomes. Our data show that the maturation and assembly of 20 S proteasomes via precursor particles is a translation-dependent gradual process, that processing of subunit proproteins takes place in these 13-16 S complexes and that subunit processing and proteasome formation occur together.
Frentzel
S
S
ZMBH, Universität Heidelberg, FRG.
Pesold-Hurt
B
B
Seelig
A
A
Kloetzel
P M
PM
D000818:Animals; D002460:Cell Line; D002499:Centrifugation, Density Gradient; D003546:Cysteine Endopeptidases / Q000737:chemistry / Q000378:metabolism*; D015180:Electrophoresis, Gel, Two-Dimensional; D004792:Enzyme Precursors / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D009097:Multienzyme Complexes / Q000737:chemistry / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D011487:Protein Conformation; D011499:Protein Processing, Post-Translational; D011506:Proteins / Q000737:chemistry / Q000378:metabolism; D013601:T-Lymphocytes / Q000378:metabolism
D004792:Enzyme Precursors; D009097:Multienzyme Complexes; D011506:Proteins; C071313:LMP-2 protein; D003546:Cysteine Endopeptidases; C077436:LMP7 protein; D046988:Proteasome Endopeptidase Complex