Structural and functional studies on a proline-rich peptide isolated from swine saliva endowed with antifungal...

Area of Science:

• Biochemistry
• Mycology
• Pharmacology

Background:

• Pathogenic fungi, such as Cryptococcus neoformans, pose significant threats to human health, necessitating the development of novel antifungal agents.
• The identification and characterization of antimicrobial peptides (AMPs) represent a promising avenue for discovering new therapeutic strategies against drug-resistant fungal strains.

Purpose of the Study:

• To isolate and characterize a proline-rich peptide from pig parotid glands.
• To evaluate the antifungal activity and spectrum of the peptide against pathogenic fungi, particularly Cryptococcus neoformans.
• To investigate the mechanism of action and safety profile of the peptide in relation to mammalian cells.

Main Methods:

• Peptide isolation and purification from pig parotid granule preparations.
• Antifungal activity assays, including determination of EC(50) values against Cryptococcus neoformans.
• Cytotoxicity and hemolytic assays using mammalian cells.
• Spectroscopic studies (Circular Dichroism, Infrared Spectroscopy) to determine peptide conformation.
• Lipid vesicle interaction studies, Neutral Red Uptake (NRU) assays, and confocal microscopy to elucidate the mechanism of action.

Main Results:

• A proline-rich peptide with a molecular mass of 2733Da was isolated.
• The peptide demonstrated significant antifungal activity against a clinical isolate of Cryptococcus neoformans, with an EC(50) of 2.2μM.
• No cytotoxic or hemolytic effects were observed in mammalian cells.
• Spectroscopic analyses indicated the peptide adopts a combination of polyproline type-II, β-turn, and unordered conformations, with a tendency towards polyproline-II helix formation at physiological temperatures.
• Experiments suggested the peptide's antifungal effect may stem from intracellular target interaction rather than membrane disruption.

Conclusions:

• The isolated proline-rich peptide possesses potent and specific antifungal activity against Cryptococcus neoformans.
• The peptide exhibits a favorable safety profile, lacking toxicity towards mammalian cells.
• The findings suggest a potential intracellular mechanism of action, differentiating it from membrane-targeting antifungals.
• This peptide represents a promising candidate for the development of novel antifungal therapeutics.