Crystal structures of the UBX domain of human UBXD7 and its complex with p97 ATPase

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• UBXD7 (UBXN7) is an adaptor protein for p97 ATPase, involved in the ubiquitin proteasome system (UPS) for degrading misfolded or damaged proteins.
• UBXD7 utilizes its UBA domain to bind ubiquitinated substrates and its UBX domain to interact with the p97 N-terminal domain (p97NTD), recruiting the p97/NPL4/UFD1 complex.

Purpose of the Study:

• To determine the crystal structures of the UBXD7 UBX domain (UBXD7^UBX) and its complex with p97NTD (p97^NTD-UBXD7^UBX).
• To elucidate the molecular basis of the interaction between UBXD7^UBX and p97^NTD.
• To investigate the potential regulatory mechanisms of the p97-UBXD7 interaction.

Main Methods:

• X-ray crystallography to obtain high-resolution structures of UBXD7^UBX and the p97^NTD-UBXD7^UBX complex.
• Isothermal titration calorimetry (ITC) to biochemically characterize the binding interaction.
• Structural superposition analysis to compare different structural states and identify potential regulatory interfaces.

Main Results:

• Crystal structures of UBXD7^UBX (2.0 Å) and the p97^NTD-UBXD7^UBX complex (2.4 Å) were determined.
• Structural and ITC data provide detailed molecular insights into the interaction between UBXD7^UBX and p97^NTD.
• Dimerization of UBXD7^UBX via disulfide bonds may inhibit p97^NTD binding, and UBXD7 may cooperatively affect p97 interaction with UFD1.

Conclusions:

• The study provides crucial structural and biochemical data on the interaction between p97^NTD and UBXD7^UBX.
• Identified potential regulatory mechanisms, including inhibition by UBXD7 dimerization and cooperative effects with UFD1.
• These findings enhance understanding of the p97-mediated protein degradation pathway.