当前位置： SCI文献检索 > BIOCHIMIE期刊下所有文献 > Degradation of oxidized proteins by the 20S proteasome.

Degradation of oxidized proteins by the 20S proteasome.

Abstract：

:Oxidatively modified proteins are continuously produced in cells by reactive oxygen and nitrogen species generated as a consequence of aerobic metabolism. During periods of oxidative stress, protein oxidation is significantly increased and may become a threat to cell survival. In eucaryotic cells the proteasome has been shown (by purification of enzymatic activity, by immunoprecipitation, and by antisense oligonucleotide studies) to selectively recognize and degrade mildly oxidized proteins in the cytosol, nucleus, and endoplasmic reticulum, thus minimizing their cytotoxicity. From in vitro studies it is evident that the 20S proteasome complex actively recognizes and degrades oxidized proteins, but the 26S proteasome, even in the presence of ATP and a reconstituted functional ubiquitinylating system, is not very effective. Furthermore, relatively mild oxidative stress rapidly (but reversibly) inactivates both the ubiquitin activating/conjugating system and 26S proteasome activity in intact cells, but does not affect 20S proteasome activity. Since mild oxidative stress actually increases proteasome-dependent proteolysis (of oxidized protein substrates) the 20S 'core' proteasome complex would appear to be responsible. Finally, new experiments indicate that conditional mutational inactivation of the E1 ubiquitin-activating enzyme does not affect the degradation of oxidized proteins, further strengthening the hypothesis that oxidatively modified proteins are degraded in an ATP-independent, and ubiquitin-independent, manner by the 20S proteasome. More severe oxidative stress causes extensive protein oxidation, directly generating protein fragments, and cross-linked and aggregated proteins, that become progressively resistant to proteolytic digestion. In fact these aggregated, cross-linked, oxidized proteins actually bind to the 20S proteasome and act as irreversible inhibitors. It is proposed that aging, and various degenerative diseases, involve increased oxidative stress (largely from damaged and electron 'leaky' mitochondria), and elevated levels of protein oxidation, cross-linking, and aggregation. Since these products of severe oxidative stress inhibit the 20S proteasome, they cause a vicious cycle of progressively worsening accumulation of cytotoxic protein oxidation products.

journal_name

Biochimie

journal_title

Biochimie

authors

Davies KJ

doi

10.1016/s0300-9084(01)01250-0

keywords:

subject

Has Abstract

pub_date

2001-03-01 00:00:00

pages

301-10

issue

3-4

eissn

0300-9084

issn

1638-6183

pii

S0300-9084(01)01250-0

journal_volume

pub_type

杂志文章,评审

在线工具

Degradation of oxidized proteins by the 20S proteasome.