Dipeptide photodegradation under copper ion influence suggests protective second-shell design in copper-binding...

Area of Science:

• Prebiotic chemistry
• Biochemistry
• Astrobiology

Background:

• The origin of copper-binding proteins is a key question in prebiotic chemistry.
• Modern copper proteins use histidine and cysteine residues for copper coordination, suggesting their early evolutionary importance.

Purpose of the Study:

• To investigate the role of ultraviolet (UV) radiation in the evolution of early copper-binding peptides.
• To explore the potential of simple amino acid sequences as primitive copper-binding motifs.

Main Methods:

• Spectroscopic analyses of copper-dipeptide interactions.
• Evaluation of peptide photostability under UV radiation.
• Assessment of copper-binding capabilities of histidine and tyrosine dipeptides.

Main Results:

• Histidine dipeptides (His₂) show strong Cu(II) binding but are UV-sensitive.
• Tyrosine dipeptides (Tyr₂) exhibit high photostability and preferential Cu(II) binding.
• His₂ and Tyr₂ likely formed cooperative complexes, with His₂ providing catalytic function and Tyr₂ offering photoprotection.

Conclusions:

• Earth's UV-rich environment likely favored cooperative copper-binding dipeptides.
• A combination of histidine and tyrosine in early peptides provided both catalytic activity and UV stability.
• This cooperative mechanism offers a plausible evolutionary pathway from simple copper-peptide complexes to functional metalloenzymes.