Secondary Structure Transitions for a Family of Amyloidogenic, Antimicrobial Uperin 3 Peptides in Contact with Sodium Dodecyl Sulfate. Issue 1 (14th January 2022)

• Record Type: Journal Article
• Authors: Prasad, Anup K.; Tiwari, Chandni; Ray, Sourav; Holden, Stephanie; Armstrong, David A.; Rosengren, K. Johan; Rodger, Alison; Panwar, Ajay S.; Martin, Lisandra L.
• Is Part Of: ChemPlusChem. Volume 87:Issue 1(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-01-14
• Subjects: antimicrobial peptide -- amyloid -- sodium dodecyl sulfate (SDS) micelle -- secondary structure; Chemistry -- Periodicals; 540.5
• DOI: 10.1002/cplu.202100408
• Languages: English
• ISSNs: 2192-6506

Abstract

Abstract: Secondary structure changes are an inherent part of antimicrobial (AMP) and amyloidogenic peptide activity, especially in close proximity to membranes, and impact the peptides' function and dysfunction roles. The formation, and stability of α‐helical components are regarded as essential 'intermediates' for both these functions. To illuminate the conformational transitions leading to amyloid formation we use short cationic AMPs, from an Australian toadlet, Uperoleia mjobergii, (Uperin 3 family, U3) and assess the impact on secondary structural elements in the presence of a membrane mimetic surfactant, sodium dodecyl sulfate (SDS). Specifically, Uperin 3. x, where x =4, 5, 6 wild‐type peptides and position seven variants for each, R7A or K7A, were investigated using a combination of experimental and simulation approaches. In water, U3 peptides remain largely unstructured as random coils, with the addition of salts initiating structural transitions leading to assembly towards amyloid. Solution NMR data show that an unstructured U3.5 wt peptide transitions in the presence of SDS to a well‐defined α‐helical structure that spans nearly the entire sequence. Circular dichroism (CD) and ThT fluorescence studies show that all six U3 peptides aggregate in solution, albeit with vastly varying rates, and a dynamic equilibrium between soluble aggregates rich in either α‐helices or β‐sheets may exist in solution. However, the addition of SDS leads to a rapid disaggregation for all peptides and stabilisation of predominantly α‐helical content in all the U3 peptides. Molecular dynamics (MD) simulations show that the adsorption of U3.5 wt/R7A peptides onto the SDS micelle is driven by Coulombic attraction between peptide cationic residues and the negatively charged sulfate head‐groups on SDS. Simulating the interactions of various kinds of β‐sheet dimers (of both U3.5 wt and its variant U3.5 R7A) with SDS micelles confirmed β‐sheet content decreases in the dimers after their attachment to the SDS micelle. Adsorbed peptides interact favourably with the hydrophobic core of the micelle, promoting intramolecular hydrogen bonds leading to stabilisation of the α‐helical structure in peptides, and resulting in a corresponding decrease in intermolecular hydrogen bonds responsible for β‐sheets. Abstract : Antimicrobial peptides from the Uperin 3 family assemble to form amyloid at different rates . Changes in secondary structure are monitored experimentally using circular dichroism and fluorescence and by molecular dynamics simulations in the presence or absence of bacterial membrane‐mimetic surfactant sodium dodecyl sulfate (SDS). Morphology and structural analysis of the fibrils has been examined using transmission electron microscopy and vibrational spectroscopy.