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Aggregation behaviour and Zn2+ binding properties of secretin
1Laboratory of Chemical Biology and Peptide Research, Clinical Research Institute of Montreal, 110 Pine Avenue West, Montreal, Quebec, Canada H2W 1R7. katharine.carpenter@arcm.ca.astra.com
Biochemistry
|December 4, 1998
Summary
Secretin forms stable hexamers in solution, with zinc ions specifically binding to histidine and aspartic acid residues, potentially aiding storage. This protein aggregation enhances its alpha-helical content and structure.
Area of Science:
- Biochemistry
- Structural Biology
- Biophysics
Background:
- Secretin is a peptide hormone involved in various physiological processes.
- Understanding secretin's structure and aggregation is crucial for elucidating its function and storage mechanisms.
Purpose of the Study:
- To investigate the solution structure and aggregation state of secretin.
- To characterize the secondary structural properties of secretin hexamers.
- To explore the potential interactions of secretin with divalent cations like Zn2+ and Ca2+.
Main Methods:
- Dynamic Light Scattering (DLS) to determine molecular size and aggregation.
- Circular Dichroism (CD) spectroscopy to assess secondary structure (alpha-helical content).
- Nuclear Magnetic Resonance (NMR) spectroscopy to analyze structural details and cation binding.
Main Results:
- Secretin forms compact hexamers in aqueous solution at millimolar concentrations.
- Alpha-helical content increases with peptide concentration, stabilizing the hexameric structure.
- Zinc ions (Zn2+) specifically bind to N-terminal His1 and Asp3 residues without disrupting helical structure, while calcium ions (Ca2+) show no interaction.
Conclusions:
- Secretin self-assembles into stable, symmetric hexamers, driven by intermolecular associations of amphipathic helical domains.
- Zinc binding to specific N-terminal residues suggests a role in secretin storage within secretory tissues.
- The findings provide insights into secretin's structural dynamics and potential regulatory mechanisms involving metal ions.