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Defining Hsp33's Redox-regulated Chaperone Activity and Mapping Conformational Changes on Hsp33 Using Hydrogen-deuterium Exchange Mass Spectrometry
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The molecular mechanism of heme loss from oxidized soluble guanylate cyclase induced by conformational change

Jie Pan1, Xiaoxue Zhang1, Hong Yuan1

  • 1Department of Chemistry & Shanghai Key laboratory of Chemical Biology for Protein Science, Fudan University, Shanghai 200433, China.

Biochimica Et Biophysica Acta
|February 16, 2016
PubMed

Insights

Oxidized soluble guanylate cyclase (sGC) readily loses its heme due to conformational changes. This study reveals how heme oxidation triggers domain movements, opening the heme pocket and leading to heme loss, a factor in cardiovascular diseases.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Cardiovascular Research

Background:

  • Heme loss from soluble guanylate cyclase (sGC) is linked to cardiovascular diseases.
  • The precise mechanism of heme loss from oxidized sGC remains unclear.

Purpose of the Study:

  • To investigate the conformational changes in sGC upon heme oxidation.
  • To understand the structural basis for heme loss in oxidized sGC.

Main Methods:

  • Utilized fluorescence resonance energy transfer (FRET) to monitor domain movements in sGC β1.
  • Labeled sGC with fluorescein arsenical helix binder (FlAsH-EDT2) to track heme-proximal structural changes.
  • Employed kinetic studies to analyze the rates of heme oxidation, conformational change, and heme loss.

Main Results:

  • Heme oxidation by ODQ induced distinct domain movements: the αF helix moved away, the PAS domain moved closer, and the helical domain moved further from the heme.
  • These synergistic conformational changes were proposed to destabilize and open the heme pocket.
  • Kinetic analysis revealed rapid heme oxidation followed by slower conformational changes and heme loss.

Conclusions:

  • The study elucidates a mechanism for heme loss in oxidized sGC driven by specific domain rearrangements.
  • Understanding these structural dynamics provides insights into the role of sGC dysfunction in cardiovascular pathology.
  • Developed a novel method to monitor heme loss kinetics using fluorescence de-quenching.

Keywords:
Conformational changeFRETFluorophoreHeme oxidation and lossSoluble guanylate cyclase

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