More Like this

1. Structural analysis of cross α-helical nanotubes provides insight into the designability of filamentous peptide nanomaterials

   https://doi.org/10.1038/s41467-020-20689-w.  

   Wang F, Gnewou O (January 2021, Nature communications)

   null (Ed.)

   The exquisite structure-function correlations observed in filamentous protein assemblies provide a paradigm for the design of synthetic peptide-based nanomaterials. However, the plasticity of quaternary structure in sequence-space and the lability of helical symmetry present significant challenges to the de novo design and structural analysis of such filaments. Here, we describe a rational approach to design self-assembling peptide nanotubes based on controlling lateral interactions between protofilaments having an unusual cross-α supramolecular architecture. Near-atomic resolution cryo-EM structural analysis of seven designed nanotubes provides insight into the designability of interfaces within these synthetic peptide assemblies and identifies a non-native structural interaction based on a pair of arginine residues. This arginine clasp motif can robustly mediate cohesive interactions between protofilaments within the cross-α nanotubes. The structure of the resultant assemblies can be controlled through the sequence and length of the peptide subunits, which generates synthetic peptide filaments of similar dimensions to flagella and pili. 

   more » « less
2. Phenol-soluble modulins PSMα3 and PSMβ2 form nanotubes that are cross-α amyloids

   https://doi.org/10.1073/pnas.2121586119  

   Kreutzberger, Mark A.; Wang, Shengyuan; Beltran, Leticia C.; Tuachi, Abraham; Zuo, Xiaobing; Egelman, Edward H.; Conticello, Vincent P. (May 2022, Proceedings of the National Academy of Sciences)

   Phenol-soluble modulins (PSMs) are peptide-based virulence factors that play significant roles in the pathogenesis of staphylococcal strains in community-associated and hospital-associated infections. In addition to cytotoxicity, PSMs display the propensity to self-assemble into fibrillar species, which may be mediated through the formation of amphipathic conformations. Here, we analyze the self-assembly behavior of two PSMs, PSMα3 and PSMβ2, which are derived from peptides expressed by methicillin-resistant Staphylococcus aureus (MRSA), a significant human pathogen. In both cases, we observed the formation of a mixture of self-assembled species including twisted filaments, helical ribbons, and nanotubes, which can reversibly interconvert in vitro. Cryo–electron microscopy structural analysis of three PSM nanotubes, two derived from PSMα3 and one from PSMβ2, revealed that the assemblies displayed remarkably similar structures based on lateral association of cross-α amyloid protofilaments. The amphipathic helical conformations of PSMα3 and PSMβ2 enforced a bilayer arrangement within the protofilaments that defined the structures of the respective PSMα3 and PSMβ2 nanotubes. We demonstrate that, similar to amyloids based on cross-β protofilaments, cross-α amyloids derived from these PSMs display polymorphism, not only in terms of the global morphology (e.g., twisted filament, helical ribbon, and nanotube) but also with respect to the number of protofilaments within a given peptide assembly. These results suggest that the folding landscape of PSM derivatives may be more complex than originally anticipated and that the assemblies are able to sample a wide range of supramolecular structural space. 

   more » « less
3. Ambidextrous helical nanotubes from self-assembly of designed helical hairpin motifs

   https://doi.org/10.1073/pnas.1903910116  

   Hughes, Spencer A.; Wang, Fengbin; Wang, Shengyuan; Kreutzberger, Mark A.; Osinski, Tomasz; Orlova, Albina; Wall, Joseph S.; Zuo, Xiaobing; Egelman, Edward H.; Conticello, Vincent P. (July 2019, Proceedings of the National Academy of Sciences)

   null (Ed.)

   Tandem repeat proteins exhibit native designability and represent potentially useful scaffolds for the construction of synthetic biomimetic assemblies. We have designed 2 synthetic peptides, HEAT_R1 and LRV_M3Δ1, based on the consensus sequences of single repeats of thermophilic HEAT (PBS_HEAT) and Leucine-Rich Variant (LRV) structural motifs, respectively. Self-assembly of the peptides afforded high-aspect ratio helical nanotubes. Cryo-electron microscopy with direct electron detection was employed to analyze the structures of the solvated filaments. The 3D reconstructions from the cryo-EM maps led to atomic models for the HEAT_R1 and LRV_M3Δ1 filaments at resolutions of 6.0 and 4.4 Å, respectively. Surprisingly, despite sequence similarity at the lateral packing interface, HEAT_R1 and LRV_M3Δ1 filaments adopt the opposite helical hand and differ significantly in helical geometry, while retaining a local conformation similar to previously characterized repeat proteins of the same class. The differences in the 2 filaments could be rationalized on the basis of differences in cohesive interactions at the lateral and axial interfaces. These structural data reinforce previous observations regarding the structural plasticity of helical protein assemblies and the need for high-resolution structural analysis. Despite these observations, the native designability of tandem repeat proteins offers the opportunity to engineer novel helical nanotubes. Moreover, the resultant nanotubes have independently addressable and chemically distinguishable interior and exterior surfaces that would facilitate applications in selective recognition, transport, and release. 

   more » « less
4. Mechanism of Cationic Peptide‐Induced Assembly of Gold Nanoparticles: Modulation of Electrostatic Repulsion

   https://doi.org/10.1002/agt2.70043  

   Lam, Benjamin; Ramji, Robert; Mullooly, Margaret; Closser, Kristina_D; Pascal, Tod_A; Jokerst, Jesse_V (April 2025, Aggregate)

   ABSTRACT The aggregation of plasmonic nanoparticles can lead to new and controllable properties useful for numerous applications. We recently showed the reversible aggregation of gold nanoparticles (AuNPs) via a small, cationic di‐arginine peptide; however, the mechanism underlying this aggregation is not yet comprehensively understood. Here, we seek insights into the intermolecular interactions of cationic peptide‐induced assembly of citrate‐capped AuNPs by empirically measuring how peptide identity impacts AuNP aggregation. We examined the nanoscale interactions between the peptides and the AuNPs via UV‐vis spectroscopy to determine the structure‐function relationship of peptide length and charge on AuNP aggregation. Careful tuning of the sequence of the di‐arginine peptide demonstrated that the mechanism of assembly is driven by a reduction in electrostatic repulsion. We show that acetylated N‐terminals and carboxylic acid C‐terminals decrease the effectiveness of the peptide in inducing AuNP aggregation. The increase in peptide size through the addition of glycine or proline units hinders aggregation and leads to less redshift. Arginine‐based peptides were also found to be more effective in assembling the AuNPs than cysteine‐based peptides of equivalent length. We also illustrate that aggregation is independent of peptide stereochemistry. Finally, we demonstrate the modulation of peptide‐AuNP behavior through changes to the pH, salt concentration, and temperature. Notably, histidine‐based and tyrosine‐based peptides could reversibly aggregate the AuNPs in response to the pH. 

   more » « less
5. Factors Affecting Secondary and Supramolecular Structures of Self‐Assembling Peptide Nanocarriers

   https://doi.org/10.1002/mabi.202100347  

   Pitz, Megan E.; Nukovic, Alexandra M.; Elpers, Margaret A.; Alexander‐Bryant, Angela A. (November 2021, Macromolecular Bioscience)

   Abstract Self‐assembling peptides are a popular vector for therapeutic cargo delivery due to their versatility, tunability, and biocompatibility. Accurately predicting secondary and supramolecular structures of self‐assembling peptides is essential for de novo peptide design. However, computational modeling of such assemblies is not yet able to accurately predict structure formation for many peptide sequences. This review identifies patterns in literature between secondary and supramolecular structures, primary sequences, and applications to provide a guide for informed peptide design. An overview of peptide structures, their applications as nanocarriers, and analytical methods for characterizing secondary and supramolecular structure is examined. A top‐down approach is then used to identify trends between peptide sequence and assembly structure from the current literature, including an analysis of the drivers at work, such as local and nonlocal sequence effects and solution conditions. 

   more » « less