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Evidence for glutamate self-capping within a peptide helix
1Department of Biochemistry, University of Iowa, Iowa City 52242, USA.
Biopolymers
|January 1, 1997
Summary
This study analyzes helical peptide chemical shifts, revealing a uniform helical structure with frayed ends. Specific alanine residues show diminished shifts, suggesting a self-capping interaction with nearby glutamate residues.
Area of Science:
- Biophysics
- Chemical Biology
- Structural Biology
Background:
- Peptide secondary structure, like helices, is crucial for biological function.
- Chemical shifts in nuclear magnetic resonance (NMR) spectroscopy provide insights into molecular conformation.
- Analyzing the thermal dependence of chemical shifts can reveal helix-coil transitions in peptides.
Purpose of the Study:
- To refine methods for analyzing chemical shift data from helical peptides.
- To investigate the helical ensemble and sequence-dependent helicity distribution.
- To explore potential interactions influencing helical structure, specifically self-capping.
Main Methods:
- Utilized two-state helix/coil transition models to analyze thermal dependence of carbonyl carbon chemical shifts.
- Improved procedures for analyzing existing chemical shift measurements of acetylW(EAAAR)3Aamide.
- Calculated difference chemical shifts to describe helicity distribution.
Main Results:
- New difference chemical shift values indicate a uniform central helical ensemble with frayed ends for most residues.
- Two alanine residues (A3 and A8) exhibited significantly diminished difference chemical shifts.
- These affected alanine residues are positioned i-4 relative to glutamate residues.
Conclusions:
- The helical peptide acetylW(EAAAR)3Aamide predominantly adopts a uniform helical structure with flexible termini.
- Diminished chemical shifts at A3 and A8 suggest a localized structural perturbation.
- A proposed self-capping interaction involving glutamate residues may explain the altered helical propensity of nearby alanines.