期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 281, 期 1, 页码 392-400出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M509126200
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资金
- Intramural NIH HHS Funding Source: Medline
Approximately 30% of polypeptides synthesized by mammalian cells are degraded with a half-life of < 10 min by proteasomes. These rapidly degraded polypeptides ( RDPs) constitute the bulk of proteasome substrates and are the principal source of viral and self- peptide ligands for major histocompatibility complex class I molecules. Here we provide evidence that similar to 75% of RDPs are degraded by the standard ubiquitin 26 S proteasome system and that their degradation is regulated by modulating Hsc70 activity in cells. Surprisingly, the remaining similar to 25% of RDPs are degraded without ubiquitylation by 20 S proteasomes independently of 19 S regulators and in a manner that is largely unaffected by modulating Hsc70 activity. This latter pathway is utilized for generating an antigenic peptide from viral-defective ribosomal products. The dichotomy in the behavior of RDPs points to a novel quality control level for nascent proteins that is independent of the well established Hsc70-ubiquitin 26 S proteasome pathway.
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