Fluorescence studies of endothelin-1.

Area of Science:

• Biophysics
• Structural Biology
• Peptide Chemistry

Background:

• Endothelin-1 is a potent vasoconstrictor peptide.
• Understanding its conformation in solution is crucial for its biological activity.
• Previous studies lacked detailed structural information in aqueous environments.

Purpose of the Study:

• To determine the solution conformation of endothelin-1.
• To investigate the spatial arrangement of key residues, specifically tyrosine and tryptophan.
• To elucidate the role of disulfide bonds and other moieties in peptide structure.

Main Methods:

• Fluorescence spectroscopy was employed to measure quantum yields and emission maxima.
• Singlet-singlet energy transfer experiments were conducted to determine intramolecular distances.
• Molecular modeling was used to compare experimental data with theoretical predictions.

Main Results:

• Tyrosine fluorescence quantum yield suggests orientation away from quenching groups.
• Tryptophan accessibility indicates solvent exposure and lack of proximity to quenching moieties.
• Singlet-singlet energy transfer yielded a Tyr(13)/Trp(21) distance of approximately 12.8 Å.
• Molecular modeling of an extended peptide showed a larger Tyr(13)/Trp(21) distance (approx. 25 Å).

Conclusions:

• Endothelin-1 adopts a conformation where C-terminal residues bend towards the bicyclic core.
• The peptide's structure in dilute aqueous solution is distinct from a fully extended model.
• These findings provide insights into endothelin-1's structure-function relationship.