A Structurally Dynamic Region of the HslU Intermediate Domain Controls Protein Degradation and ATP Hydrolysis

Structure. 2016 Oct 4;24(10):1766-1777. doi: 10.1016/j.str.2016.08.012. Epub 2016 Sep 22.

Abstract

The I domain of HslU sits above the AAA+ ring and forms a funnel-like entry to the axial pore, where protein substrates are engaged, unfolded, and translocated into HslV for degradation. The L199Q I-domain substitution, which was originally reported as a loss-of-function mutation, resides in a segment that appears to adopt multiple conformations as electron density is not observed in HslU and HslUV crystal structures. The L199Q sequence change does not alter the structure of the AAA+ ring or its interactions with HslV but increases I-domain susceptibility to limited endoproteolysis. Notably, the L199Q mutation increases the rate of ATP hydrolysis substantially, results in slower degradation of some proteins but faster degradation of other substrates, and markedly changes the preference of HslUV for initiating degradation at the N or C terminus of model substrates. Thus, a structurally dynamic region of the I domain plays a key role in controlling protein degradation by HslUV.

Keywords: AAA+ protease; ATP-dependent degradation; HslUV protease; allosteric control.

MeSH terms

  • Adenosine Triphosphate / chemistry*
  • Crystallography, X-Ray
  • Endopeptidase Clp / chemistry*
  • Endopeptidase Clp / genetics*
  • Escherichia coli / chemistry
  • Escherichia coli / enzymology*
  • Escherichia coli / genetics
  • Escherichia coli Proteins / chemistry*
  • Escherichia coli Proteins / genetics*
  • Hydrolysis
  • Microscopy, Electron
  • Models, Molecular
  • Mutation*
  • Protein Domains
  • Proteolysis
  • Substrate Specificity

Substances

  • ClpYQ protease, E coli
  • Escherichia coli Proteins
  • Adenosine Triphosphate
  • Endopeptidase Clp