Electrostatic stabilization in methionine aminopeptidase from hyperthermophile Pyrococcus furiosus

Area of Science:

• Biochemistry
• Protein Science
• Enzymology

Background:

• Methionine aminopeptidase (MAP) plays a crucial role in protein synthesis.
• Hyperthermophilic enzymes often possess superior thermostability.
• Understanding the factors contributing to enzyme thermostability is vital for biotechnology and protein engineering.

Purpose of the Study:

• To investigate the contribution of electrostatic interactions to the exceptional thermostability of methionine aminopeptidase from the hyperthermophile Pyrococcus furiosus (PfMAP).
• To elucidate the effect of pH and salt concentration on the thermal denaturation of PfMAP.

Main Methods:

• Differential scanning calorimetry (DSC) was employed to study the thermal denaturation of PfMAP.
• Circular dichroism (CD) spectroscopy and ultracentrifugation were used to analyze protein structure.
• Comparative analysis of PfMAP and Escherichia coli MAP (EcMAP) sequences and structures.

Main Results:

• PfMAP demonstrated high thermostability with a denaturation temperature of 106.2°C at pH 10.2.
• In acidic conditions (pH 3-4), denaturation was irreversible, with transition temperatures decreasing at lower pH.
• In the presence of KCl (10-100 mM) at pH 3.2, DSC revealed two denaturation peaks, indicating stabilization of the native form and formation of a molten globule-like state.
• Structural comparison suggested that four extra short-range ion pairs in PfMAP are critical for its superior thermostability.

Conclusions:

• Attractive electrostatic interactions are essential for stabilizing the native structure of PfMAP.
• Potassium chloride (KCl) promotes the formation and stabilization of a molten globule-like state in PfMAP.
• The superior thermostability of PfMAP is attributed to specific structural features, including short-range ion pairs.