Design of Non-Cysteine-Containing Antimicrobial β-Hairpins: Structure−Activity Relationship Studies with Linear Protegrin-1 Analogues
- 27 September 2002
- journal article
- Published by American Chemical Society (ACS) in Biochemistry
- Vol. 41 (42), 12835-12842
- https://doi.org/10.1021/bi026127d
Abstract
Protegrins are short, cationic peptides that display potent, broad-spectrum antimicrobial activity. PG-1, the first of the five natural analogues discovered, forms a rigid antiparallel two-stranded beta-sheet that is stabilized by two disulfide bonds. The two strands of the sheet are linked by a short two-residue loop segment. Removal of the disulfide bridges (e.g., in Cys --> Ala analogues) is known to cause marked loss of antimicrobial activity. We have used basic principles of beta-hairpin design to develop linear analogues of PG-1 that lack cysteine but nevertheless display PG-1-like activity. Our most potent reengineered molecules contain three essential design features: (i) the four cysteine residues of PG-1 are replaced by residues that have high propensity for beta-strand conformation, (ii) D-proline is placed at the i + 1 position of the reverse turn to promote a type II' beta-turn, and (iii) amino functionality is incorporated at the gamma-carbon of the D-proline residue to mimic the charge distribution of the natural beta-hairpin. Structural studies revealed that the antimicrobial potency of the non-disulfide-bonded peptides can be correlated to the stability of the beta-hairpin conformations they adopt in aqueous solution. The presence of 150 mM NaCl was found to have little effect on the antimicrobial activity of PG-1, but one of our linear analogues loses some potency under these high salt conditions. Despite this discrepancy in salt sensitivity, NMR and CD data indicate that neither PG-1 nor our linear analogue experiences a significant decrease in beta-hairpin conformational stability in the presence of 150 mM NaCl. Thus, salt inactivation is not due to destabilization of the beta-hairpin conformation. Furthermore, our results show that beta-sheet design principles can be used to replace conformation-stabilizing disulfide bridges with noncovalent conformation-stabilizing features.Keywords
This publication has 20 references indexed in Scilit:
- Interplay between hydrophobic cluster and loop propensity in β-hairpin formationJournal of Molecular Biology, 2001
- Insights on β-Hairpin Stability in Aqueous Solution from Peptides with Enforced Type I‘ and Type II‘ β-TurnsJournal of the American Chemical Society, 1997
- Synthesis and Solution Structure of the Antimicrobial Peptide Protegrin‐1European Journal of Biochemistry, 1996
- Change in membrane permeability induced by protegrin 1: implication of disulphide bridges for pore formationFEBS Letters, 1996
- Stereochemical Requirements for β-Hairpin Formation: Model Studies with Four-Residue Peptides and DepsipeptidesJournal of the American Chemical Society, 1996
- Analysis of Two-residue Turns in ProteinsJournal of Molecular Biology, 1994
- Protegrins: leukocyte antimicrobial peptides that combine features of corticostatic defensins and tachyplesinsFEBS Letters, 1993
- Relationship between nuclear magnetic resonance chemical shift and protein secondary structureJournal of Molecular Biology, 1991
- Conformation of β-hairpins in protein structuresJournal of Molecular Biology, 1989
- Analysis and prediction of the different types of β-turn in proteinsJournal of Molecular Biology, 1988