期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 102, 期 5, 页码 1390-1395出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0409634102
关键词
ClpP; CIpX; energy-dependent proteolysis; protein unfolding; titin I27 domain
资金
- NIAID NIH HHS [R01 AI015706, R37 AI015706, AI-15706] Funding Source: Medline
Energy-dependent proteases, such as ClpXP, are responsible for the regulated destruction of proteins in all cells. AAA+ ATPases in these proteases bind protein substrates and power their mechanical denaturation and subsequent translocation into a secluded degradation chamber where polypeptide cleavage occurs. Here, we show that model unfolded substrates are engaged rapidly by ClpXP and are then spooled into the degradation chamber at a rate proportional to their length. Degradation and competition studies indicate that ClpXP initially binds native and unfolded substrates similarly. However, stable native substrates then partition between frequent release and infrequent denaturation, with only the latter step resulting in committed degradation. During degradation of a fusion protein with three tandem native domains, partially degraded species with one and two intact domains accumulated. These processed proteins were not bound to the enzyme, showing that release can occur even after translocation and degradation of a substrate have commenced. The release of stable substrates and committed engagement of denatured or unstable native molecules ensures that ClpXP degrades less stable substrates in a population preferentially. This mechanism prevents trapping of the enzyme in futile degradation attempts and ensures that the energy of ATP hydrolysis is used efficiently for protein degradation.
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