Ubiquitin recognition by the human TSG101 protein

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• The TSG101 UEV domain is crucial for HIV-1 budding and vacuolar protein sorting (VPS).
• It binds ubiquitylated proteins for sorting into multivesicular bodies (MVBs).
• This interaction is vital for delivering proteins to lysosomes via MVB fusion.

Purpose of the Study:

• To determine the crystal structure of the TSG101 UEV domain bound to ubiquitin.
• To elucidate the molecular basis of the TSG101 UEV-ubiquitin interaction.
• To understand how TSG101 UEV binds ubiquitin and peptide ligands.

Main Methods:

• X-ray crystallography was used to obtain the structure at 2.0 A resolution.
• Site-directed mutagenesis was employed to disrupt the UEV-ubiquitin interface.
• Comparative analysis with other UEV and E2 protein domains was performed.

Main Results:

• The crystal structure reveals TSG101 UEV binding to ubiquitin via the Ile44 surface and an adjacent loop.
• Mutations disrupting this interface inhibit MVB sorting.
• The structure explains independent binding of ubiquitin and peptide ligands.
• Comparison with related proteins shows conserved structure and ubiquitin binding but distinct interfaces.

Conclusions:

• The TSG101 UEV-ubiquitin interaction interface is critical for MVB sorting.
• The structure provides insights into the dual ligand-binding capabilities of TSG101 UEV.
• UEV and E2 domains share structural and functional conservation in ubiquitin binding, yet utilize diverse interfaces.