Serum stable natural peptides designed by mRNA display.

Area of Science:

• Biochemistry
• Molecular Biology
• Drug Discovery

Background:

• Peptides composed of natural amino acids often lack therapeutic potential due to instability against proteases and peptidases.
• Proteolytic cleavage can be specific, suggesting that naturally occurring functional sequences might possess inherent resistance.
• The signaling protein Gαi1 serves as a target for exploring protease-resistant functional peptides.

Purpose of the Study:

• To investigate the potential for enhancing the protease resistance of functional peptides while maintaining their biological activity.
• To identify natural peptide analogues with significantly improved stability against proteolytic degradation.
• To explore the application of these enhanced peptides in therapeutic contexts.

Main Methods:

• A two-step in vitro selection strategy was employed, combining protease degradation with functional selection.
• An initial peptide library was treated with chymotrypsin to enrich for protease-resistant sequences.
• Messenger RNA (mRNA) display was used for positive selection of peptides that retained binding to Gαi1 after protease treatment.

Main Results:

• Selected peptides exhibited a 100-400 fold increase in resistance to chymotrypsin compared to the parental library.
• Surprisingly, enhanced chymotrypsin resistance correlated with a ~100 fold improvement in stability within human serum.
• Mechanistic studies revealed that improved stability resulted from reduced cleavage rates (kcat) and weaker protease interactions (Km).

Conclusions:

• Optimizing the primary amino acid sequence of functional peptides can dramatically enhance their hydrolytic stability.
• This strategy offers a viable method for developing therapeutically relevant peptides from natural sequences.
• The findings suggest a powerful approach for improving peptide drug candidates' pharmacokinetic properties.