Proline-glutamate chimera’s side chain conformation directs the type of β-hairpin structure

Abstract

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 IYSNPcis -E DGTWT (P1_Pcis-E) and IYSNP(trans-E)DGTWT (P1_Ptrans-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_Pcis-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_Ptrans-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.

Design and structural characterisation of monomeric water-soluble α-helix and β-hairpin peptides: State-of-the-art

“…One approach takes into account the essential role of the loop region (section 5.1.1) and incorporates non-natural sequences at the loop region able to induce β-hairpin formation [263,264]. For instance, DPheAbz (Abz = 2-aminobenzoic acid) turn motif has been used to stabilise β-hairpin formation in an non-polar water-insoluble peptide, as well as in amphipathic peptides, which have antimicrobial activity [265].…”

The Crucial Role of S‐oxidation State on the Selectivity and Reaction Rate of the 1,3‐Dipolar Cycloaddition of Azomethine Ylides and Homochiral Thiazolines

“…Proline analogs [38][39][40] have been of singular interest for the development of new peptide-based therapeutics [41][42][43][44][45] and the elucidation of biological active conformations involved in molecular recognition (Scheme 2). [46,47] The 3-mercaptoprolines derivatives can be considered as proline-cysteine analogs and 4-mercaptoprolines can be considered as (homo)cysteine-proline analogs.…”