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Halocin H4 is activated through cleavage by halolysin HlyR4
Shaoxing Chen1,2,3, Yongpei Dai1, Juntao Ke1
1College of Life Sciences, Anhui Normal University, Wuhu, China.
Applied and Environmental Microbiology
|March 6, 2024
Summary
Halocin H4 (HalH4) requires cleavage by halolysin R4 (HlyR4) for its antimicrobial activity. The C-terminus of HalH4 (CTH4) is the active peptide, showing broad-spectrum inhibition against haloarchaea and bacteria.
Area of Science:
- Microbiology and Molecular Biology
- Extremophile Biology
- Antimicrobial Peptide Research
Background:
- Halocins are antimicrobial peptides produced by haloarchaea, crucial for inter-species competition.
- Halocin H4 (HalH4) from Haloferax mediterranei is difficult to express and activate heterologously.
- Haloarchaeal secreted proteases play a role in modifying extracellular proteins.
Purpose of the Study:
- To investigate the activation mechanism of Halocin H4 (HalH4) and identify the active antimicrobial component.
- To explore the role of secreted proteases, specifically halolysin R4 (HlyR4), in HalH4 activity.
- To determine the functional importance of different HalH4 domains for its antihaloarchaeal activity.
Main Methods:
- Heterologous expression of halH4 in Escherichia coli.
- Proteolytic cleavage of HalH4 by halolysin R4 (HlyR4).
- Mass spectrometry to identify cleavage products and active peptides.
- Site-directed mutagenesis (C115G) and domain deletion (trans-membrane region) to assess functional impact.
- Antimicrobial activity assays against various haloarchaeal and bacterial species.
Main Results:
- Heterologous expression of HalH4 in E. coli did not yield active halocin without specific processing.
- Cleavage by HlyR4 activated HalH4's antihaloarchaeal activity, with the C-terminus (CTH4) identified as the active peptide.
- Specific mutations (C115G) and deletion of the trans-membrane region significantly reduced HalH4 activity, indicating domain importance.
- The CTH4 peptide demonstrated broad-spectrum antimicrobial activity against multiple haloarchaeal and bacterial genera.
Conclusions:
- Halocin H4 activation is dependent on proteolytic cleavage by secreted proteases like HlyR4, a novel finding for halocins.
- The C-terminal region of HalH4 is essential for its antimicrobial function, likely through membrane pore formation.
- This study reveals a complex interplay between halocins and proteases in haloarchaeal antagonistic interactions.
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