Rabaptin-5 is a direct effector of the small GTPase Rab5 in endocytic membrane fusion

Cell. 1995 Nov 3;83(3):423-32. doi: 10.1016/0092-8674(95)90120-5.


We have identified a novel 100 kDa coiled-coil protein, rabaptin-5, that specifically interacts with the GTP form of the small GTPase Rab5, a potent regulator of endocytic transport. It is mainly cytosolic, but a fraction colocalizes with Rab5 to early endosomes. Expression of a GTPase-deficient Rab5 mutant enhances the binding of rabaptin-5 to enlarged endosomes. Overexpression of rabaptin-5 alone is sufficient to promote expansion of early endosomes. Rab5 recruits rabaptin-5 to purified early endosomes in a GTP-dependent manner, demonstrating functional similarities with other members of the Ras superfamily. Immunodepletion of rabaptin-5 from cytosol strongly inhibits Rab5-dependent early endosome fusion. Rabaptin-5 is thus a Rab effector required for membrane docking and fusion.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Cell-Free System
  • Cytosol / chemistry
  • DNA, Complementary / genetics
  • Endocytosis / physiology*
  • Endosomes / physiology
  • Fungal Proteins / physiology
  • GTP Phosphohydrolases / physiology*
  • GTP-Binding Proteins / physiology*
  • Gene Expression / physiology
  • Gene Library
  • Genetic Testing
  • Intracellular Membranes / chemistry
  • Intracellular Membranes / physiology
  • Membrane Fusion / physiology*
  • Membrane Proteins / analysis
  • Membrane Proteins / physiology*
  • Molecular Sequence Data
  • Protein Binding / physiology
  • Protein Structure, Secondary
  • Vesicular Transport Proteins*
  • Yeasts / physiology
  • rab5 GTP-Binding Proteins


  • DNA, Complementary
  • Fungal Proteins
  • Membrane Proteins
  • Vesicular Transport Proteins
  • GTP Phosphohydrolases
  • GTP-Binding Proteins
  • rab5 GTP-Binding Proteins

Associated data

  • GENBANK/X91141