Molten globule monomers in human superoxide dismutase

Area of Science:

• Biochemistry
• Biophysics
• Protein Folding Dynamics

Background:

• Cu/Zn human superoxide dismutase (HSOD) is crucial for cellular defense against reactive oxygen species.
• Understanding HSOD's structural dynamics is vital for comprehending its enzymatic function and potential dysfunction in disease.

Purpose of the Study:

• To investigate the structural microheterogeneity and unfolding pathways of HSOD.
• To identify and characterize any intermediate states during HSOD denaturation.

Main Methods:

• Time-resolved fluorescence decay and anisotropy measurements at varying temperatures and denaturant concentrations.
• Circular dichroism (CD) spectroscopy in amide and aromatic regions during guanidinium hydrochloride denaturation.
• Global analysis of fluorescence decay data across denaturant concentrations.

Main Results:

• Fluorescence decay analysis indicated structural microheterogeneity within HSOD.
• CD spectroscopy and fluorescence data revealed an intermediate during HSOD unfolding induced by guanidinium hydrochloride.
• This intermediate was characterized as a monomeric molten globule state.

Conclusions:

• HSOD exhibits significant structural microheterogeneity.
• A distinct monomeric molten globule intermediate is present during guanidinium hydrochloride-induced unfolding.
• These findings provide insights into the complex folding landscape of HSOD.