Pnserpin: A Novel Serine Protease Inhibitor from Extremophile Pyrobaculum neutrophilum

Area of Science:

• Biochemistry
• Molecular Biology
• Extremophile Research

Background:

• Serine protease inhibitors (serpins) are crucial regulators of serine proteases.
• Prokaryotic serpins, particularly from extremophiles, are underrepresented in current research.
• Understanding thermophilic serpins offers insights into protein stability and function at high temperatures.

Purpose of the Study:

• To overexpress, purify, and characterize Pnserpin, a putative serpin from the thermophile Pyrobaculum neutrophilum.
• To investigate the inhibitory activity and mechanism of Pnserpin against various serine proteases.
• To explore the structural properties and thermal stability of Pnserpin.

Main Methods:

• Overexpression and purification of Pnserpin in Escherichia coli.
• Enzyme inhibition assays across a temperature range (20-100 °C).
• SDS-PAGE to analyze protease-inhibitor complex formation.
• Homology modeling and molecular dynamic simulations for structural prediction.

Main Results:

• Pnserpin irreversibly inhibits chymotrypsin-, trypsin-, elastase-, and subtilisin-like proteases in a concentration-dependent manner.
• Inhibitory activity of Pnserpin increases with temperature, as indicated by a decreasing stoichiometry of inhibition.
• Pnserpin forms SDS-resistant covalent complexes with target proteases.
• Structural modeling predicts a stable, common serpin fold for Pnserpin.

Conclusions:

• Pnserpin is a functional thermophilic serine protease inhibitor with enhanced activity at higher temperatures.
• The study provides valuable structural and functional data on a novel extremophilic serpin.
• This research expands the understanding of serpin diversity and function in extreme environments.