The AAA ATPase p97/VCP interacts with its alternative co-factors, Ufd1-Npl4 and p47, through a common bipartite binding mechanism.
The AAA ATPase p97/VCP forms complexes with different adapters to fulfill distinct cellular functions. We analyzed the structural organization of the Ufd1-Npl4 adapter complex and its interaction with p97 and compared it with another adapter, p47. We found that the binary Ufd1-Npl4 complex forms a heterodimer that cooperatively interacts with p97 via a bipartite binding mechanism. Binding site 1 (BS1) is a short hydrophobic stretch in the C-terminal domain of Ufd1. The second binding site is located at the N terminus of Npl4 and is activated upon binding of Ufd1 to Npl4. It consists of about 80 amino acids that are predicted to form a ubiquitin fold domain (UBD). Despite the lack of overall homology between Ufd1-Npl4 and p47, both adapters use identical binding mechanisms. Like the ubiquitin fold ubiquitin regulatory X (UBX) domain in p47, the Npl4-UBD interacts with p97 via the loop between its strands 3 and 4 and a conserved arginine in strand 1. Furthermore, we identified a region in p47 homologous to Ufd1-BS1. The UBD/UBX and the BS1 of both adapters interact with p97 independently, whereas homologous binding sites in both adapters compete for binding to p97. In contrast to p47, however, Ufd1-Npl4 does not regulate the ATPase activity of p97; nor does a variant of p47 that contains both binding sites but lacks the N-terminal domains. Therefore, the binding sites alone do not regulate p97 directly but rather serve as anchor points to position adapter-specific domains at critical locations to modulate p97-mediated reactions.
Bruderer
Roland M
RM
Swiss Federal School of Technology, Institute of Biochemistry, ETH Honggerberg HPM, Zurich 8093, Switzerland.
Brasseur
Catherine
C
Meyer
Hemmo H
HH
D000251:Adenosine Triphosphatases; D000818:Animals; D001665:Binding Sites; D002352:Carrier Proteins / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000378:metabolism*; D015536:Down-Regulation; D009154:Mutation; D028861:Nuclear Pore Complex Proteins / Q000235:genetics / Q000378:metabolism; D029543:Nucleocytoplasmic Transport Proteins; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D052067:Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins; D000074405:Valosin Containing Protein; D033921:Vesicular Transport Proteins / Q000378:metabolism*
D002352:Carrier Proteins; D018797:Cell Cycle Proteins; C104361:NPL4 protein, S cerevisiae; C495985:Nploc4 protein, rat; C498751:Nsfl1c protein, rat; D028861:Nuclear Pore Complex Proteins; D029543:Nucleocytoplasmic Transport Proteins; D011506:Proteins; D029701:Saccharomyces cerevisiae Proteins; D052067:Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins; C491496:Ufd1 protein, rat; D033921:Vesicular Transport Proteins; D000251:Adenosine Triphosphatases; C000614177:CDC48 protein, S cerevisiae; D000074405:Valosin Containing Protein; C000614180:Vcp protein, rat