Stabilization of human pancreatic ribonuclease through mutation at its N-terminal edge

Area of Science:

• Biochemistry
• Protein Engineering
• Enzyme Kinetics

Background:

• Enzyme stability is critical for recombinant toxin efficacy, as degradation can prevent target cell delivery.
• Human pancreatic ribonuclease variants are being explored for their potential to induce cytotoxicity in tumor cells.
• Protein modifications, while potentially enhancing function, can compromise enzyme stability.

Purpose of the Study:

• To investigate the impact of N-terminal amino acid alterations on the thermal stability of human pancreatic ribonuclease.
• To determine the correlation between N-terminal modifications and the helical propensity of the protein's first alpha-helix.
• To assess the effect of C-terminal residue deletion on enzyme stability.

Main Methods:

• Site-directed mutagenesis to introduce amino acid substitutions at the N-terminus.
• Analysis of thermal stability using established biochemical assays.
• Circular dichroism spectroscopy to evaluate changes in helical propensity.
• Deletion mutagenesis to remove C-terminal residues.

Main Results:

• Amino acid substitutions at the N-terminus significantly increased the thermal stability of human pancreatic ribonuclease.
• The observed increase in thermostability correlated directly with enhanced helical propensity in the N-terminal alpha-helix.
• Deletion of the final four C-terminal residues did not alter the enzyme's thermal stability.

Conclusions:

• N-terminal modifications are a viable strategy to enhance the stability of human pancreatic ribonuclease variants.
• Understanding the relationship between N-terminal helical propensity and stability facilitates the rational design of more robust enzyme therapeutics.
• These findings provide a foundation for engineering cytotoxic human pancreatic ribonuclease with improved stability for cancer therapy.