Cyclic tetrapeptides with sequences related to HC toxin. Conformations and cation binding

Area of Science:

• * Biochemistry and Molecular Biology
• * Peptide Chemistry and Conformation
• * Toxicology and Chemical Biology

Background:

• * HC toxin is a cyclic peptide phytotoxin produced by the fungus *Cochliobolus heterostrophus*.
• * Understanding the structure-activity relationship of HC toxin is crucial for its toxicological and agricultural applications.
• * Previous studies have suggested complex conformational dynamics in cyclic peptides.

Purpose of the Study:

• * To investigate the conformational properties of HC toxin-related peptides.
• * To explore the interaction of these peptides with magnesium cations.
• * To establish a link between peptide conformation, magnesium binding, and biological activity.

Main Methods:

• * Synthesis and characterization of peptides with sequences related to HC toxin.
• * Spectroscopic techniques (e.g., NMR, CD spectroscopy) to determine peptide conformation.
• * Analysis of peptide-metal ion complexation using spectroscopic and binding assays.

Main Results:

• * HC toxin-related peptides were found to adopt a stable conformation stabilized by three gamma turns.
• * A direct correlation between specific spectroscopic characteristics and the observed peptide conformation was established.
• * Peptides demonstrated the ability to complex with Mg++ cations, leading to a significant transconformation of the peptide backbone.

Conclusions:

• * The conformational flexibility of HC toxin-related peptides is influenced by metal ion binding.
• * The observed Mg++ induced transconformation is a key factor potentially modulating the biological activity of the toxin.
• * This study provides insights into the molecular mechanisms underlying HC toxin's phytotoxicity.