Conformational diversity of bradykinin in aqueous solution

Area of Science:

• Biochemistry
• Structural Biology
• Spectroscopy

Background:

• Bradykinin is a peptide hormone with diverse physiological roles.
• Understanding its solution structure is crucial for elucidating its function.
• Previous structural data in aqueous solution remains limited.

Purpose of the Study:

• To characterize the solution structure of bradykinin and its analogs using high-field proton nuclear magnetic resonance (NMR).
• To investigate the conformational dynamics and potential structural features of bradykinin.
• To explore interactions between bradykinin and lipid-like molecules.

Main Methods:

• Recording and assignment of 600-MHz proton NMR spectra for bradykinin and analogs.
• Utilizing pH variation, spin-spin decoupling, and chemical shift correlations for spectral assignment.
• Analyzing spin-spin coupling constants to infer conformational flexibility.

Main Results:

• Complete assignment of proton NMR spectra for bradykinin and modified analogs.
• Analysis indicates bradykinin exists in a rapid equilibrium of multiple conformers.
• No persistent structural features like beta turns or internal hydrogen bonds were detected.
• High concentrations of lipids induced spectral changes, suggesting specific interactions with proline-7 and phenylalanine-8.

Conclusions:

• Bradykinin exhibits significant conformational flexibility in aqueous solution.
• The peptide does not adopt a single, stable conformation.
• Lipid interactions can influence bradykinin's side-chain conformation and binding sites.