Rab35/ACAP2 and Rab35/RUSC2 Complex Structures Reveal Molecular Basis for Effector Recognition by Rab35 GTPase

Structure. 2019 May 7;27(5):729-740.e3. doi: 10.1016/j.str.2019.02.008. Epub 2019 Mar 21.

Abstract

Rab35, a master regulator of membrane trafficking, regulates diverse cellular processes and is associated with various human diseases. Although a number of effectors have been identified, the molecular basis of Rab35-effector interactions remains unclear. Here, we provide the high-resolution crystal structures of Rab35 in complex with its two specific effectors ACAP2 and RUSC2, respectively. In the Rab35/ACAP2 complex structure, Rab35 binds to the terminal ankyrin repeat and a C-terminal extended α helix of ACAP2, revealing a previously uncharacterized binding mode both for Rabs and ankyrin repeats. In the Rab35/RUSC2 complex structure, Arg1015 of RUSC2 functions as a "pseudo-arginine finger" that stabilizes the GTP-bound Rab35, thus facilitating the assembly of Rab35/RUSC2 complex. The structural analysis allows us to design specific Rab35 mutants capable of eliminating Rab35/ACAP2 and Rab35/RUSC2 interactions, but not interfering with other effector bindings. The atomic structures also offer possible explanations to disease-associated mutants identified at the Rab35-effector interfaces.

Keywords: ACAP2; RUSC2; Rab-effector; Rab35; crystal structure; membrane trafficking.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ADP-Ribosylation Factors / chemistry
  • Arginine / chemistry
  • Carrier Proteins / chemistry*
  • HEK293 Cells
  • Humans
  • Membrane Proteins / chemistry*
  • Mutation*
  • Protein Binding
  • Protein Domains
  • Protein Structure, Secondary
  • rab GTP-Binding Proteins / chemistry*

Substances

  • ACAP2 protein, human
  • Carrier Proteins
  • Membrane Proteins
  • RUSC2 protein, human
  • Arginine
  • RAB35 protein, human
  • ADP-Ribosylation Factors
  • rab GTP-Binding Proteins