3QE0

A Galpha-i1 P-loop mutation prevents transition to the activated state


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 3 Å
  • R-Value Free: 0.292 
  • R-Value Work: 0.247 

wwPDB Validation 3D Report Full Report


This is version 1.1 of the entry. See complete history

Literature

A P-loop Mutation in Galpha Subunits Prevents Transition to the Active State: Implications for G-protein Signaling in Fungal Pathogenesis

Bosch, D.E.Willard, F.S.Ramanujam, R.Kimple, A.J.Willard, M.D.Naqvi, N.I.Siderovski, D.P.

(2012) Plos Pathog. 8: e1002553-e1002553

  • DOI: 10.1371/journal.ppat.1002553
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 
  • Heterotrimeric G-proteins are molecular switches integral to a panoply of different physiological responses that many organisms make to environmental cues. The switch from inactive to active Gαβγ heterotrimer relies on nucleotide cycling by the Gα su ...

    Heterotrimeric G-proteins are molecular switches integral to a panoply of different physiological responses that many organisms make to environmental cues. The switch from inactive to active Gαβγ heterotrimer relies on nucleotide cycling by the Gα subunit: exchange of GTP for GDP activates Gα, whereas its intrinsic enzymatic activity catalyzes GTP hydrolysis to GDP and inorganic phosphate, thereby reverting Gα to its inactive state. In several genetic studies of filamentous fungi, such as the rice blast fungus Magnaporthe oryzae, a G42R mutation in the phosphate-binding loop of Gα subunits is assumed to be GTPase-deficient and thus constitutively active. Here, we demonstrate that Gα(G42R) mutants are not GTPase deficient, but rather incapable of achieving the activated conformation. Two crystal structure models suggest that Arg-42 prevents a typical switch region conformational change upon Gα(i1)(G42R) binding to GDP·AlF(4)(-) or GTP, but rotameric flexibility at this locus allows for unperturbed GTP hydrolysis. Gα(G42R) mutants do not engage the active state-selective peptide KB-1753 nor RGS domains with high affinity, but instead favor interaction with Gβγ and GoLoco motifs in any nucleotide state. The corresponding Gα(q)(G48R) mutant is not constitutively active in cells and responds poorly to aluminum tetrafluoride activation. Comparative analyses of M. oryzae strains harboring either G42R or GTPase-deficient Q/L mutations in the Gα subunits MagA or MagB illustrate functional differences in environmental cue processing and intracellular signaling outcomes between these two Gα mutants, thus demonstrating the in vivo functional divergence of G42R and activating G-protein mutants.


    Related Citations: 
    • Structure of Galpha(i1) bound to a GDP-selective peptide provides insight into guanine nucleotide exchange.
      Johnston, C.A.,Willard, F.S.,Jezyk, M.R.,Fredericks, Z.,Bodor, E.T.,Jones, M.B.,Blaesius, R.,Watts, V.J.,Harden, T.K.,Sondek, J.,Ramer, J.K.,Siderovski, D.P.
      (2005) Structure 13: 1069


    Organizational Affiliation

    Department of Pharmacology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Guanine nucleotide-binding protein G(i) subunit alpha-1
A, B, C
325Homo sapiensMutation(s): 1 
Gene Names: GNAI1
Find proteins for P63096 (Homo sapiens)
Go to Gene View: GNAI1
Go to UniProtKB:  P63096
Entity ID: 2
MoleculeChainsSequence LengthOrganismDetails
KB752 peptide
G, F
16N/AMutation(s): 0 
Protein Feature View is not available: No corresponding UniProt sequence found.
Small Molecules
Ligands 2 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
GDP
Query on GDP

Download SDF File 
Download CCD File 
A, B, C
GUANOSINE-5'-DIPHOSPHATE
C10 H15 N5 O11 P2
QGWNDRXFNXRZMB-UUOKFMHZSA-N
 Ligand Interaction
MG
Query on MG

Download SDF File 
Download CCD File 
A, B, C
MAGNESIUM ION
Mg
JLVVSXFLKOJNIY-UHFFFAOYSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 3 Å
  • R-Value Free: 0.292 
  • R-Value Work: 0.247 
  • Space Group: P 61 2 2
Unit Cell:
Length (Å)Angle (°)
a = 106.637α = 90.00
b = 106.637β = 90.00
c = 455.062γ = 120.00
Software Package:
Software NamePurpose
PHENIXrefinement
PHASERphasing
HKL-2000data scaling
HKL-2000data collection
HKL-2000data reduction

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2012-01-25
    Type: Initial release
  • Version 1.1: 2012-03-14
    Type: Database references