Isolation and
Characterization of the PA28-associated Proteasome
WANG Guo-Chun*,
WU Dong-Hai
( Department of Clinical Immunology & Rheumatology, China Japan
Friendship Hospital, Beijing 100029, China )
Abstract Proteasome,
a high molecular weight multicatalytic protease complex,is responsible for most
non lysosomal intracellular protein degradations. The proteasome is composed of
a 20 S catalytic core (20 S proteasome) and additional subunits, that are
thought to be involved in the recognition of proteins or in the regulation of
the protease activity of the proteasome. A 180 kD activator, named PA28 or Reg,
associates with the 20 S proteasome and enhance the peptidase activity of the
20 S core enzyme. In this report, the biochemical isolation of the
PA28-associated proteasome subset from the 20 S proteasome core is
described,based on gradient anion exchange chromatography. The PA28-20 S
proteasome subset, isolated from EBV-transformed B cells, was found to be
highly enriched in the LMP2 (low molecular weight protein) subset, whereas no
LMP2 was detected by immunoblotting in the PA28-20 S proteasome subset. The
close correlation of expression of PA28 and LMP2, two interferon (IFN)-γ
inducible proteasome components,on a single proteasome subset suggests that
PA28 may associate preferentially with LMP2-containing proteasomes, and/or this
subset may have a specific role in the processing of environmental antigens.
Key words proteasome； PA28 activator； LMP2
*Corresponding author： Tel, 86-10-64221122-4542； e-mail, [email protected]