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Conformationally Regulated Peptide Bond Cleavage in Bradykinin
Daniel R Fuller1, Christopher R Conant1, Tarick J El-Baba1
1Department of Chemistry , Indiana University , Bloomington , Indiana 47405 , United States.
Journal of the American Chemical Society
|July 21, 2018
Summary
Bradykinin (BK) undergoes a unique nonenzymatic cleavage at the Pro2-Pro3 bond, triggered by temperature-induced protonation and isomerization. This intrinsic pathway, resistant to human enzymes, offers insights into peptide processing and antigenicity.
Area of Science:
- Biochemistry
- Chemical Physics
- Analytical Chemistry
Background:
- Bradykinin (BK) is a peptide with known biological functions.
- Understanding peptide stability and processing is crucial for drug development and biological studies.
- Intrinsic peptide cleavage pathways can offer insights into biological resistance mechanisms.
Purpose of the Study:
- To investigate the conformational stabilities of different bradykinin (BK) conformations using ion mobility and mass spectrometry.
- To elucidate the mechanism of a novel, nonenzymatic Pro2-Pro3 bond cleavage in BK.
- To determine the thermodynamic parameters of the transition states involved in BK processing.
Main Methods:
- Ion mobility spectrometry coupled with mass spectrometry (IM-MS).
- Temperature-dependent kinetic studies.
- Analysis of protonation reactions and conformational changes.
Main Results:
- Elevated temperatures induce a slow protonation reaction ([BK+2H]2+ → [BK+3H]3+) regulated by Arg1-Pro2 trans → cis isomerization.
- The all-cis [BK+3H]3+ conformation spontaneously cleaves the Pro2-Pro3 bond with high specificity.
- This cleavage occurs via multiple intermediates, regulated by Arg1-Pro2 isomerization, and is biologically resistant.
- Transition state thermochemistry for protonation and bond cleavage was determined.
Conclusions:
- A novel nonenzymatic cleavage pathway for bradykinin at the Pro2-Pro3 bond is identified.
- This pathway is regulated by Arg1-Pro2 trans → cis isomerization and protonation.
- The biological resistance to this intrinsic processing pathway has implications for peptide antigenicity.
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