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Structural and Functional Analysis of Peptides Derived from KEX2-Processed Repeat Proteins in Agaricomycetes Using Reverse Genetics and Peptidomics

Summary

Researchers studied special peptides made by mushrooms that are processed by fungal enzymes called KEX2 and KEX1. They developed a method to find and identify these peptides in mushroom tissues and confirmed they exist in both laboratory and edible mushroom species like shiitake and oyster mushrooms. When they removed the genes for these processing enzymes, the mushrooms had problems growing and forming fruiting bodies, suggesting these enzymes have important roles beyond just processing these specific peptides.

Background

KEX2-processed repeat proteins (KEPs) are a recently defined class of fungal precursor proteins containing multiple peptide cores flanked by KEX2 protease cleavage sites. Genome mining has revealed that KEPs are widespread in the fungal kingdom, but their functions remain largely unknown. Some KEP-derived peptides have known bioactivities including antimicrobial and virulence factor properties.

Objective

To present the first in-depth structural and functional analysis of KEPs in a basidiomycete model organism. The study aimed to establish a detection protocol for KEP-derived peptides and characterize their roles in fungal growth and development using reverse genetics and peptidomics approaches.

Results

Several KEP-derived peptides were confirmed in C. cinerea and three edible mushroom species (Lentinula edodes, Pleurotus ostreatus, and Pleurotus eryngii). Peptide expression showed tissue-specific patterns with some peptides exclusively detected in fruiting bodies. While kep knockouts showed no detectable phenotype, kex gene knockouts caused defects in mycelial growth and fruiting body formation, suggesting KEX proteases target multiple substrates beyond KEPs.

Conclusion

The study establishes a novel protocol for detecting KEP-derived peptides in fungi through combined reverse genetics and peptidomics. Results suggest KEP-derived peptides may play roles in biotic interactions rather than axenic growth. The KEX proteases that process KEPs target diverse substrates important for mycelial growth and differentiation in agaricomycetes.
  • Published in:Microbiology Spectrum,
  • Study Type:Experimental Research,
  • Source: PMID: 36314921, DOI: 10.1128/spectrum.02021-22
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