Phosphoglycerate Kinase Can Adopt Topologically Misfolded Forms That Are More Stable Than Its Native State

Area of Science:

• Biochemistry
• Structural Biology
• Molecular Biology

Background:

• Globular proteins' native states are generally considered the most stable conformations.
• The thermodynamic hypothesis explains reversible protein refolding after denaturation.
• This study challenges the assumption of native state stability.

Purpose of the Study:

• To investigate counterexamples to the thermodynamic hypothesis in protein folding.
• To characterize an unusual misfolded form of E. coli phosphoglycerate kinase (PGK).
• To explore the role of topology in protein misfolding and stability.

Main Methods:

• Protein refolding experiments involving dilution from denaturant.
• Kinetic stability assays measuring resistance to thermal and detergent denaturation.
• Circularization of PGK to assess the impact of protein termini on misfolding.

Main Results:

• E. coli PGK refolded into a kinetically stable, native-like misfolded form, more stable than its native state.
• This misfolded form exhibited resistance to thermal and detergent-induced denaturation.
• Circularization of PGK prevented the formation of these kinetically stable misfolded states, indicating a topological basis.

Conclusions:

• A misfolded protein can be more kinetically stable than its native state without aggregation or amyloid formation.
• Protein topology plays a critical role in the formation of kinetically stable misfolded states.
• Topologically misfolded proteins represent a potential challenge to cellular proteostasis networks.