Distinct Rab-binding domains mediate the interaction of Rabaptin-5 with GTP-bound Rab4 and Rab5

EMBO J. 1998 Apr 1;17(7):1941-51. doi: 10.1093/emboj/17.7.1941.


Rabaptin-5 functions as an effector for the small GTPase Rab5, a regulator of endocytosis and early endosome fusion. We have searched for structural determinants that confer functional specificity on Rabaptin-5. Here we report that native cytosolic Rabaptin-5 is present in a homodimeric state and dimerization depends upon the presence of its coiled-coil predicted sequences. A 73 residue C-terminal region of Rabaptin-5 is necessary and sufficient both for the interaction with Rab5 and for Rab5-dependent recruitment of the protein on early endosomes. Surprisingly, we uncovered the presence of an additional Rab-binding domain at the N-terminus of Rabaptin-5. This domain mediates the direct interaction with the GTP-bound form of Rab4, a small GTPase that has been implicated in recycling from early endosomes to the cell surface. Based on these results, we propose that Rabaptin-5 functions as a molecular linker between two sequentially acting GTPases to coordinate endocytic and recycling traffic.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Cattle
  • Cell Line
  • Cricetinae
  • Cytosol / chemistry
  • Dimerization
  • Endosomes / metabolism
  • GTP-Binding Proteins / analysis
  • GTP-Binding Proteins / metabolism*
  • Guanosine Triphosphate / metabolism*
  • HeLa Cells
  • Humans
  • Membrane Proteins / analysis
  • Membrane Proteins / chemistry
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Molecular Sequence Data
  • Protein Binding
  • Protein Structure, Secondary
  • Recombinant Fusion Proteins
  • Sequence Alignment
  • Vesicular Transport Proteins*
  • rab4 GTP-Binding Proteins
  • rab5 GTP-Binding Proteins


  • Membrane Proteins
  • RABEP1 protein, human
  • Recombinant Fusion Proteins
  • Vesicular Transport Proteins
  • Guanosine Triphosphate
  • GTP-Binding Proteins
  • rab4 GTP-Binding Proteins
  • rab5 GTP-Binding Proteins