Proline-glutamate chimera’s side chain conformation directs the type of β-hairpin structure
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Our aim was to study the impact of two proline chimeras, containing a glutamic acid side chain in cis- or trans-configuration, on secondary structure formation. We further investigated to what extent the configuration of the side chain contributes to the overall peptide conformation. We used a 10 residue peptide (IYSNPDGTWT) that forms a β-hairpin in water. The turn-forming proline was substituted with either a cis- or trans-proline-glutamic acid chimera, resulting in the peptides IYSNP cis -E DGTWT (P1_P cis-E ) and IYSNP trans -E DGTWT (P1_P trans-E ). We studied the conformation of the modified peptides by circular dichroism (CD) and NMR-spectroscopy, and SEC/static light scattering (SLS) analysis. NMR analysis reveals that the modified peptides maintain the β-hairpin conformation in aqueous solution. At 5 °C and pH 4.3, the peptide (P1_P cis-E ) was found to adopt two coexisting β-hairpin conformations (2:2 β-hairpin, and 3:5 β-hairpin). In contrast to that, the peptide (P1_P trans-E ) adopts a 2:2 β-hairpin that exists in equilibrium with a 4:4 β-hairpin conformation. The adoption of ordered β-hairpin structures for both modified peptides could be confirmed by CD spectroscopy, while SEC/SLS analysis showed a monomeric oligomerization state for all three investigated peptides. With the combination of several NMR methods, we were able to elucidate that even small alterations in the side chain conformation of the proline-glutamate chimera (cis or trans) can significantly influence the conformation of the adopted β-hairpin.
KeywordsProline chimera β-Hairpin conformation β-Turn Conformational analysis CD NMR
High performance liquid chromatography
Size exclusion chromatography
cis-Proline glutamate chimera
trans-proline glutamate chimera
Nuclear magnetic resonance
- 1H NMR
Proton nuclear magnetic resonance
Total correlation spectroscopy
Nuclear Overhauser effect
Nuclear Overhauser effect spectroscopy
Rotating frame nuclear Overhauser effect spectroscopy
Solid phase peptide synthesis
The authors thank the Center for International Cooperation and the Dahlem Research School of Freie Universität Berlin for funding.
Conflict of interest
The authors declare that they have no conflict of interest.
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