Identification of an iron-hepcidin complex

Area of Science:

• Biochemistry
• Molecular Biology
• Physiology

Background:

• Hepcidin is identified as a liver-expressed antimicrobial peptide and a key regulator of iron homoeostasis.
• Hepcidin is proposed as the 'iron hormone' that interacts with ferroportin to control iron import.
• Previous studies emphasized the mature 25-mer peptide, overlooking potential functions of its maturation process.

Purpose of the Study:

• To investigate the formation and characteristics of iron-hepcidin complexes.
• To explore the potential roles of iron binding in hepcidin function and maturation.
• To elucidate the structural and functional implications of iron interaction with hepcidin.

Main Methods:

• Purification of native hepcidin from urine.
• Computer modelling and construction of a three-dimensional hepcidin model.
• Spectroscopic analyses including Mass Spectrometry (MS), UV/visible absorbance, Circular Dichroism (CD), and Electron Paramagnetic Resonance (EPR) spectroscopy.

Main Results:

• Demonstrated the formation of iron-hepcidin complexes from purified native hepcidin.
• Identified monoferric hepcidin and minor amounts of di- and tri-ferric complexes using MS.
• Spectroscopic studies confirmed iron-binding events at physiological pH and identified the ferric state (Fe(3+)) with potential tetrahedral sulfur coordination.

Conclusions:

• Iron binding to hepcidin is a significant characteristic of the peptide.
• Iron-hepcidin complexes may play a regulatory role in pro-hepcidin maturation.
• Iron binding could be crucial for the interaction between hepcidin and the iron transporter ferroportin.