Crystal structures of the scaffolding protein LGN reveal the general mechanism by which GoLoco binding motifs inhibit the release of GDP from Gαi

J Biol Chem. 2012 Oct 26;287(44):36766-76. doi: 10.1074/jbc.M112.391607. Epub 2012 Sep 5.

Abstract

GoLoco (GL) motif-containing proteins regulate G protein signaling by binding to Gα subunit and acting as guanine nucleotide dissociation inhibitors. GLs of LGN are also known to bind the GDP form of Gα(i/o) during asymmetric cell division. Here, we show that the C-terminal GL domain of LGN binds four molecules of Gα(i)·GDP. The crystal structures of Gα(i)·GDP in complex with LGN GL3 and GL4, respectively, reveal distinct GL/Gα(i) interaction features when compared with the only high resolution structure known with GL/Gα(i) interaction between RGS14 and Gα(i1.) Only a few residues C-terminal to the conserved GL sequence are required for LGN GLs to bind to Gα(i)·GDP. A highly conserved "double Arg finger" sequence (RΨ(D/E)(D/E)QR) is responsible for LGN GL to bind to GDP bound to Gα(i). Together with the sequence alignment, we suggest that the LGN GL/Gα(i) interaction represents a general binding mode between GL motifs and Gα(i). We also show that LGN GLs are potent guanine nucleotide dissociation inhibitors.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Amino Acid Substitution
  • Animals
  • Binding Sites
  • Carrier Proteins / chemistry*
  • Carrier Proteins / genetics
  • Cell Cycle Proteins
  • Conserved Sequence
  • Crystallography, X-Ray
  • GTP-Binding Protein alpha Subunit, Gi2 / chemistry*
  • Guanosine Diphosphate / chemistry*
  • Humans
  • Hydrogen Bonding
  • Mice
  • Models, Molecular
  • Molecular Sequence Data
  • Protein Binding
  • Protein Interaction Domains and Motifs
  • Protein Structure, Secondary
  • Thermodynamics
  • Titrimetry

Substances

  • Carrier Proteins
  • Cell Cycle Proteins
  • LGN protein, mouse
  • Guanosine Diphosphate
  • GTP-Binding Protein alpha Subunit, Gi2

Associated data

  • PDB/4G5O
  • PDB/4G5Q
  • PDB/4G5R
  • PDB/4G5S