title: Distinct structural elements of the adaptor ClpS are required for regulating degradation by ClpAP.
abstract: Adaptor proteins modify substrate recognition by AAA+ ATPases. We examined how the adaptor ClpS regulates substrate choice by the Escherichia coli protease ClpAP. Binding of six ClpS molecules to a ClpA hexamer enhanced N-end-rule substrate degradation and inhibited ssrA-tagged protein proteolysis. Substoichiometric ClpS binding allowed intermediate degradation of both substrate types, revealing that adaptor stoichiometry influences substrate choice. ClpS controls substrate selection using distinct mechanisms. The N-terminal segment is essential for delivering N-end-rule substrates but dispensable for ssrA-protein inhibition. We tested existing models for ClpS action and found that ClpS does not block recognition of ssrA-tagged substrates by steric occlusion and that adaptor-mediated tethering of N-end-rule substrates to ClpAP was insufficient to explain facilitated delivery. We propose that ClpS functions, at least in part, as an allosteric effector of ClpAP, broadening our understanding of how AAA+ adaptors control substrate selection.
authors.affiliation: Department of Biology, 68-523, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
authors.forename: Jennifer Y
authors.initials: JY
authors.lastname: Hou
authors.forename: Robert T
authors.initials: RT
authors.lastname: Sauer
authors.forename: Tania A
authors.initials: TA
authors.lastname: Baker
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000737:chemistry*; D064211:Connectin; D049071:Endopeptidase Clp / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006868:Hydrolysis; D008954:Models, Biological; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000737:chemistry; D011485:Protein Binding; D011494:Protein Kinases / Q000737:chemistry; D011499:Protein Processing, Post-Translational; D012329:RNA, Bacterial / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D002352:Carrier Proteins; C454820:ClpS protein, E coli; D064211:Connectin; D029968:Escherichia coli Proteins; D009124:Muscle Proteins; D012329:RNA, Bacterial; C096222:tmRNA; D049452:Green Fluorescent Proteins; D000255:Adenosine Triphosphate; D011494:Protein Kinases; C483568:ClpA protease, E coli; C483572:ClpP protease, E coli; D049071:Endopeptidase Clp; D000251:Adenosine Triphosphatases