The I domain of the AAA+ HslUV protease coordinates substrate binding, ATP hydrolysis, and protein degradation

Protein Sci. 2012 Feb;21(2):188-98. doi: 10.1002/pro.2001. Epub 2012 Jan 4.


In the AAA+ HslUV protease, substrates are bound and unfolded by a ring hexamer of HslU, before translocation through an axial pore and into the HslV degradation chamber. Here, we show that the N-terminal residues of an Arc substrate initially bind in the HslU axial pore, with key contacts mediated by a pore loop that is highly conserved in all AAA+ unfoldases. Disordered loops from the six intermediate domains of the HslU hexamer project into a funnel-shaped cavity above the pore and are positioned to contact protein substrates. Mutations in these I-domain loops increase K(M) and decrease V(max) for degradation, increase the mobility of bound substrates, and prevent substrate stimulation of ATP hydrolysis. HslU-ΔI has negligible ATPase activity. Thus, the I domain plays an active role in coordinating substrate binding, ATP hydrolysis, and protein degradation by the HslUV proteolytic machine.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / metabolism*
  • Endopeptidase Clp / chemistry*
  • Endopeptidase Clp / genetics
  • Endopeptidase Clp / metabolism*
  • Escherichia coli Proteins / chemistry*
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism*
  • Hydrolysis
  • Models, Biological
  • Models, Molecular
  • Mutation / physiology
  • Protein Binding / genetics
  • Protein Binding / physiology
  • Protein Interaction Domains and Motifs / genetics
  • Protein Interaction Domains and Motifs / physiology*
  • Protein Transport / genetics
  • Proteolysis*
  • Substrate Specificity / genetics


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