Monoubiquitylation of GGA3 by hVPS18 regulates its ubiquitin-binding ability

Biochem Biophys Res Commun. 2006 Nov 10;350(1):82-90. doi: 10.1016/j.bbrc.2006.09.013. Epub 2006 Sep 15.


GGAs (Golgi-localizing, gamma-adaptin ear domain homology, ADP-ribosylation factor (ARF)-binding proteins), constitute a family of monomeric adaptor proteins and are associated with protein trafficking from the trans-Golgi network to endosomes. Here, we show that GGA3 is monoubiquitylated by a RING-H2 type-ubiquitin ligase hVPS18 (human homologue of vacuolar protein sorting 18). By in vitro ubiquitylation assays, we have identified lysine 258 in the GAT domain as a major ubiquitylation site that resides adjacent to the ubiquitin-binding site. The ubiquitylation is abolished by a mutation in either the GAT domain or ubiquitin that disrupts the GAT-ubiquitin interaction, indicating that the ubiquitin binding is a prerequisite for the ubiquitylation. Furthermore, the GAT domain ubiquitylated by hVPS18 no longer binds to ubiquitin, indicating that ubiquitylation negatively regulates the ubiquitin-binding ability of the GAT domain. These results suggest that the ubiquitin binding and ubiquitylation of GGA3-GAT domain are mutually inseparable through a ubiquitin ligase activity of hVPS18.

MeSH terms

  • ADP-Ribosylation Factors / genetics
  • ADP-Ribosylation Factors / metabolism*
  • Adaptor Proteins, Vesicular Transport / genetics
  • Adaptor Proteins, Vesicular Transport / metabolism*
  • Binding Sites
  • Crystallography, X-Ray
  • HeLa Cells
  • Humans
  • Lysine / genetics
  • Lysine / metabolism
  • Models, Molecular
  • Protein Binding
  • Protein Structure, Quaternary
  • Ubiquitin / metabolism*
  • Ubiquitin-Protein Ligases / metabolism
  • Vesicular Transport Proteins / genetics
  • Vesicular Transport Proteins / metabolism*


  • Adaptor Proteins, Vesicular Transport
  • GGA adaptor proteins
  • Ubiquitin
  • VPS18 protein, human
  • Vesicular Transport Proteins
  • Ubiquitin-Protein Ligases
  • ADP-Ribosylation Factors
  • Lysine