ATP hydrolysis by the proteasome regulatory complex PAN serves multiple functions in protein degradation.
To clarify the role of ATP in proteolysis, we studied archaeal 20S proteasomes and the PAN (proteasome-activating nucleotidase) regulatory complex, a homolog of the eukaryotic 19S ATPases. PAN's ATPase activity was stimulated similarly by globular (GFPssrA) and unfolded (casein) substrates, and by the ssrA recognition peptide. Denaturation of GFPssrA did not accelerate its degradation or eliminate the requirement for PAN and ATP. During degradation of one molecule of globular or unfolded substrates, 300-400 ATP molecules were hydrolyzed. An N-terminal deletion in the 20S alpha subunits caused opening of the substrate-entry channel and rapid degradation of unfolded proteins without PAN; however, degradation of globular GFPssrA still required PAN's ATPase activity, even after PAN-catalyzed unfolding. Thus, substrate binding activates ATP hydrolysis, which promotes three processes: substrate unfolding, gate opening in the 20S, and protein translocation.
Benaroudj
Nadia
N
Harvard Medical School, Department of Cell Biology, 240 Longwood Avenue, Boston, MA 02115, USA.
Zwickl
Peter
P
Seemüller
Erika
E
Baumeister
Wolfgang
W
Goldberg
Alfred L
AL
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D019843:Archaeal Proteins / Q000235:genetics / Q000378:metabolism*; D003546:Cysteine Endopeptidases / Q000737:chemistry / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D009097:Multienzyme Complexes / Q000737:chemistry / Q000378:metabolism*; D010455:Peptides / Q000235:genetics / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex; D011485:Protein Binding; D011489:Protein Denaturation; D017510:Protein Folding; D021381:Protein Transport / Q000502:physiology; D011506:Proteins / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
D019843:Archaeal Proteins; D008164:Luminescent Proteins; D009097:Multienzyme Complexes; D010455:Peptides; D011506:Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D000255:Adenosine Triphosphate; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D000251:Adenosine Triphosphatases; C420334:PAN enzyme