Structural basis for monoubiquitin recognition by the Ede1 UBA domain

Area of Science:

• Cell Biology
• Structural Biology
• Biochemistry

Background:

• Monoubiquitination targets cell surface receptors for lysosomal degradation via endocytosis.
• The yeast Ede1 protein, essential for endocytic internalization, recognizes monoubiquitinated proteins using its ubiquitin-associated (UBA) domain.
• Conserved UBA domains interact with ubiquitin, but recognition mechanisms may vary across proteins.

Purpose of the Study:

• To elucidate the structural basis of monoubiquitin recognition by the yeast Ede1 UBA domain.
• To investigate the determinants of the Ede1 UBA domain-ubiquitin interaction through mutational analysis.

Main Methods:

• Solution structure determination of the Ede1 UBA domain in complex with monoubiquitin.
• Site-directed mutagenesis to probe protein-protein interactions and binding affinities.

Main Results:

• The Ede1 UBA domain adopts a three-helix bundle structure.
• Ubiquitin is bound via a largely hydrophobic surface, similar to Dsk2 UBA and Cue2 CUE domains.
• The interaction mode differs from proposed models for hHR23A UBA domains.
• Mutational analysis identified key affinity determinants and a surprising negative determinant in the wild-type Ede1 protein.

Conclusions:

• The Ede1 UBA domain-monoubiquitin interaction is structurally characterized, revealing conserved and unique features.
• Optimal function of monoubiquitin-binding proteins in endocytosis may not solely depend on high-affinity interactions.