Structure, Function, and Dynamics of the Gα Binding Domain of Ric-8A

Structure. 2019 Jul 2;27(7):1137-1147.e5. doi: 10.1016/j.str.2019.04.013. Epub 2019 May 30.


Ric-8A is a 530-amino acid cytoplasmic molecular chaperone and guanine nucleotide exchange factor (GEF) for i, q, and 12/13 classes of heterortrimeric G protein alpha subunits (Gα). We report the 2.2-Å crystal structure of the Ric-8A Gα-binding domain with GEF activity, residues 1-452, and is phosphorylated at Ser435 and Thr440. Residues 1-429 adopt a superhelical fold comprised of Armadillo (ARM) and HEAT repeats, and the C terminus is disordered. One of the phosphorylated residues potentially binds to a basic cluster in an ARM motif. Amino acid sequence conservation and published hydrogen-deuterium exchange data indicate repeats 3 through 6 to be a putative Gα-binding surface. Normal mode modeling of small-angle X-ray scattering data indicates that phosphorylation induces relative rotation between repeats 1-4, 5-6, and 7-9. 2D 1H-15N-TROSY spectra of [2H,15N]-labeled Gαi1 in the presence of R452 reveals chemical shift perturbations of the C terminus and Gαi1 residues involved in nucleotide binding.

Keywords: X-ray crystallography; guanine nucleotide exchange factor; heteronuclear nuclear magnetic resonance; heterotrimeric G protein; molecular chaperone; protein dynamics; protein structure; small-angle X-ray scattering.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Binding Sites
  • Cloning, Molecular
  • Crystallography, X-Ray
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • GTP-Binding Protein alpha Subunits, Gi-Go / chemistry*
  • GTP-Binding Protein alpha Subunits, Gi-Go / genetics
  • GTP-Binding Protein alpha Subunits, Gi-Go / metabolism
  • Gene Expression
  • Genetic Vectors / chemistry
  • Genetic Vectors / metabolism
  • Guanine Nucleotide Exchange Factors / chemistry*
  • Guanine Nucleotide Exchange Factors / genetics
  • Guanine Nucleotide Exchange Factors / metabolism
  • Guanosine Triphosphate
  • Histidine / genetics
  • Histidine / metabolism
  • Models, Molecular
  • Mutation
  • Nuclear Proteins / chemistry*
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism
  • Oligopeptides / genetics
  • Oligopeptides / metabolism
  • Protein Binding
  • Protein Conformation, alpha-Helical
  • Protein Conformation, beta-Strand
  • Protein Interaction Domains and Motifs
  • Protein Multimerization
  • Rats
  • Recombinant Fusion Proteins / chemistry*
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism


  • Guanine Nucleotide Exchange Factors
  • His-His-His-His-His-His
  • Nuclear Proteins
  • Oligopeptides
  • Recombinant Fusion Proteins
  • Ric8a protein, rat
  • Histidine
  • Guanosine Triphosphate
  • GTP-Binding Protein alpha Subunits, Gi-Go