April 2014
Volume 55, Issue 13
Free
ARVO Annual Meeting Abstract  |   April 2014
Analysis of the complex between transducin-α and UNC119 by Small Angle X-ray Scattering (SAXS)
Author Affiliations & Notes
  • Pallavi Cheguru
    Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA
  • Anurima Majumder
    Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA
  • Gopalakrishna Kota
    Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA
  • Lokesh Gakhar
    Biochemistry, University of Iowa, Iowa City, IA
  • Nikolai Artemyev
    Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA
  • Footnotes
    Commercial Relationships Pallavi Cheguru, None; Anurima Majumder, None; Gopalakrishna Kota, None; Lokesh Gakhar, None; Nikolai Artemyev, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science April 2014, Vol.55, 418. doi:
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      Pallavi Cheguru, Anurima Majumder, Gopalakrishna Kota, Lokesh Gakhar, Nikolai Artemyev; Analysis of the complex between transducin-α and UNC119 by Small Angle X-ray Scattering (SAXS). Invest. Ophthalmol. Vis. Sci. 2014;55(13):418.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract
 
Purpose
 

UNC119 is a protein partner of transducin-α (Gαt) shown to be important for transducin trafficking in rods. We have examined the solution structure of the UNC119/ Gαt complex by SAXS in order to gain insights into the mechanism of transducin trafficking.

 
Methods
 

UNC119 and myristoylated chimeric Gαt were co-expressed in E. coli. A highly pure UNC119/ Gαt complex with excellent monodispersity was obtained by a three-step chromatographic procedure. SAXS data on the UNC119/ Gαt complex were collected using different exposure times of synchrotron radiation and varying concentrations of the complex. Combined rigid-body/ab initio modeling against the SAXS data was performed using known atomic structures of UNC119 and Gαt.

 
Results
 

Analyses of the scattering curves for the protein complex indicated a radius of gyration (Rg) of 34.7 Å and a maximum particle dimension (Dmax) of 117 Å. The model of the UNC119/ Gαt complex with the best fit to the SAXS data indicated rotation and bending of the N-terminal α-helix (αN) of Gαt from its position in the structure of heterotrimeric Gt. This conformation of αN allows a considerably more compact overall conformation of the complex in which the two molecules have additional interactions involving the β3-β4 loop and the α5-helix/C-terminus of Gαt.

 
Conclusions
 

The SAXS solution structure of the UNC119/ Gαt complex suggests a novel interface between UNC119 and Gαt. This interface is potentially critical to the ability of UNC119 to solubilize transducin from the membrane and facilitate its trafficking.

 
Keywords: 648 photoreceptors • 659 protein structure/function • 714 signal transduction  
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