THE COMPARATIVE ANALYSIS OF EXTRA- AND INTRACELLULAR PROTEASOMES
FROM K562 CELL LINE
Yu. Ia. Zaykova,1 V. A. Kulichkova,1 Yu. B. Ermolaeva,1 L. N. Gause,2 A. S. Tsimokha 1, *
1 Institute of Cytology RAS, St. Petersburg, and
2 N. K. Koltsov Institute of Development Biology RAS, Moscow;
* e-mail: atsimokha@mail.cytspb.rssi.ru
The comparative analysis of peptidase activities of extra- and intracellular proteasomes was carried out. Here
we have shown that excreted proteasomes exhibit higher chymotrypsin-type and lower tripsin-like peptidase
activities that cytoplasmic particles. Posttranslational modifications (PTMs) of 20S proteasomal subunits were
revealed by immunoblotting techniques. We have observed the difference in PTMs of associated with enzymatic
activities subunits β2, β5 and α5 of extracellular and cytoplasmic proteasomes. Proteasomal subunits α2, 4, 7
and β7 also had a variety of PTMs. The phosphorylation level of excreted proteasomes was lower compared to
that of the intracellular ones. This observation strongly suggests the involvement of this PTM in the regulation
of proteasomes excretion from cells.
Key words: extracellular proteasomes, peptidase activities, phosphorylation, posttranslational modifications,
serine, threonine, tyrosine
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