1BH2

A326S MUTANT OF AN INHIBITORY ALPHA SUBUNIT


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.1 Å
  • R-Value Free: 0.250 
  • R-Value Work: 0.190 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

The A326S mutant of Gialpha1 as an approximation of the receptor-bound state.

Posner, B.A.Mixon, M.B.Wall, M.A.Sprang, S.R.Gilman, A.G.

(1998) J.Biol.Chem. 273: 21752-21758


  • PubMed Abstract: 
  • Agonist-bound heptahelical receptors activate heterotrimeric G proteins by catalyzing exchange of GDP for GTP on their alpha subunits. In search of an approximation of the receptor-alpha subunit complex, we have considered the properties of A326S Gia ...

    Agonist-bound heptahelical receptors activate heterotrimeric G proteins by catalyzing exchange of GDP for GTP on their alpha subunits. In search of an approximation of the receptor-alpha subunit complex, we have considered the properties of A326S Gialpha1, a mutation discovered originally in Gsalpha (Iiri, T., Herzmark, P., Nakamoto, J. M., Van Dop, C., and Bourne, H. R. (1994) Nature 371, 164-168) that mimics the effect of receptor on nucleotide exchange. The mutation accelerates dissociation of GDP from the alphai1beta1gamma2 heterotrimer by 250-fold. Nevertheless, affinity of mutant Gialpha1 for GTPgammaS is high in the presence of Mg2+, and the mutation has no effect on the intrinsic GTPase activity of the alpha subunit. The mutation also uncouples two activities of betagamma: stabilization of the GDP-bound alpha subunit (which is retained) and retardation of GDP dissociation from the heterotrimer (which is lost). For wild-type and mutant Gialpha1, beta gamma prevents irreversible inactivation of the alpha subunit at 30 degreesC. However, the mutation accelerates irreversible inactivation of alpha at 37 degreesC despite the presence of beta gamma. Structurally, the mutation weakens affinity for GTPgammaS by steric crowding: a 2-fold increase in the number of close contacts between the protein and the purine ring of the nucleotide. By contrast, we observe no differences in structure at the GDP binding site between wild-type heterotrimers and those containing A326S Gialpha1. However, the GDP binding site is only partially occupied in crystals of G protein heterotrimers containing A326S Gialpha1. In contrast to original speculations about the structural correlates of receptor-catalyzed nucleotide exchange, rapid dissociation of GDP can be observed in the absence of substantial structural alteration of a Galpha subunit in the GDP-bound state.


    Organizational Affiliation

    Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75235-9041, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
GUANINE NUCLEOTIDE-BINDING PROTEIN
A
315Rattus norvegicusGene Names: Gnai1 (Gnai-1)
Find proteins for P10824 (Rattus norvegicus)
Go to UniProtKB:  P10824
Small Molecules
Ligands 2 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
MG
Query on MG

Download SDF File 
Download CCD File 
A
MAGNESIUM ION
Mg
JLVVSXFLKOJNIY-UHFFFAOYSA-N
 Ligand Interaction
GSP
Query on GSP

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Download CCD File 
A
5'-GUANOSINE-DIPHOSPHATE-MONOTHIOPHOSPHATE
C10 H16 N5 O13 P3 S
XOFLBQFBSOEHOG-UUOKFMHZSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.1 Å
  • R-Value Free: 0.250 
  • R-Value Work: 0.190 
  • Space Group: P 32 2 1
Unit Cell:
Length (Å)Angle (°)
a = 79.584α = 90.00
b = 79.584β = 90.00
c = 105.556γ = 120.00
Software Package:
Software NamePurpose
X-PLORrefinement
SCALEPACKdata scaling
AMoREphasing
DENZOdata reduction

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 1998-11-04
    Type: Initial release
  • Version 1.1: 2008-03-24
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance