title: The I domain of the AAA+ HslUV protease coordinates substrate binding, ATP hydrolysis, and protein degradation.
abstract: 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.
authors.affiliation: Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Shankar
authors.initials: S
authors.lastname: Sundar
authors.forename: Tania A
authors.initials: TA
authors.lastname: Baker
authors.forename: Robert T
authors.initials: RT
authors.lastname: Sauer
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D049071:Endopeptidase Clp / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006868:Hydrolysis; D008954:Models, Biological; D008958:Models, Molecular; D009154:Mutation / Q000502:physiology; D011485:Protein Binding / Q000235:genetics / Q000502:physiology; D054730:Protein Interaction Domains and Motifs / Q000235:genetics / Q000502:physiology*; D021381:Protein Transport / Q000235:genetics; D059748:Proteolysis; D013379:Substrate Specificity / Q000235:genetics
chemical_list: C483566:ClpYQ protease, E coli; D029968:Escherichia coli Proteins; D000255:Adenosine Triphosphate; D049071:Endopeptidase Clp
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