221 results found
Wang Z, Zhao S, Li Y, et al., 2021, RssB-mediated sigma(S) Activation is Regulated by a Two-Tier Mechanism via Phosphorylation and Adaptor Protein - IraD, JOURNAL OF MOLECULAR BIOLOGY, Vol: 433, ISSN: 0022-2836
Darby JF, Vidler LR, Simpson PJ, et al., 2020, Solution structure of the Hop TPR2A domain and investigation of target druggability by NMR, biochemical and in silico approaches, SCIENTIFIC REPORTS, Vol: 10, ISSN: 2045-2322
Murphy P, Xu Y, Rouse SL, et al., 2020, Functional 3D architecture in an intrinsically disordered E3 ligase domain facilitates ubiquitin transfer, NATURE COMMUNICATIONS, Vol: 11, ISSN: 2041-1723
Broncel M, Dominicus C, Vigetti L, et al., 2020, Profiling of myristoylation in Toxoplasma gondii reveals an N-myristoylated protein important for host cell penetration, ELIFE, Vol: 9, ISSN: 2050-084X
Sewell L, Stylianou F, Xu Y, et al., 2020, NMR insights into the pre-amyloid ensemble and secretion targeting of the curli subunit CsgA, Scientific Reports, Vol: 10, ISSN: 2045-2322
The biofilms of Enterobacteriaceae are fortified by assembly of curli amyloid fibres on the cell surface. Curli not only provides structural reinforcement, but also facilitates surface adhesion. To prevent toxic intracellular accumulation of amyloid precipitate, secretion of the major curli subunit, CsgA, is tightly regulated. In this work, we have employed solution state NMR spectroscopy to characterise the structural ensemble of the pre-fibrillar state of CsgA within the bacterial periplasm, and upon recruitment to the curli pore, CsgG, and the secretion chaperone, CsgE. We show that the N-terminal targeting sequence (N) of CsgA binds specifically to CsgG and that its subsequent sequestration induces a marked transition in the conformational ensemble, which is coupled to a preference for CsgE binding. These observations lead us to suggest a sequential model for binding and structural rearrangement of CsgA at the periplasmic face of the secretion machinery.
Sheppard D, Berry J-L, Denise R, et al., 2020, The major subunit of widespread competence pili exhibits a novel and conserved type IV pilin fold, Journal of Biological Chemistry, Vol: 295, Pages: 6594-6604, ISSN: 0021-9258
<jats:p>Type IV filaments (T4F), which are helical assemblies of type IV pilins, constitute a superfamily of filamentous nanomachines virtually ubiquitous in prokaryotes that mediate a wide variety of functions. The competence (Com) pilus is a widespread T4F, mediating DNA uptake (the first step in natural transformation) in bacteria with one membrane (monoderms), an important mechanism of horizontal gene transfer. Here, we report the results of genomic, phylogenetic, and structural analyses of ComGC, the major pilin subunit of Com pili. By performing a global comparative analysis, we show that Com pili genes are virtually ubiquitous in Bacilli, a major monoderm class of Firmicutes. This also revealed that ComGC displays extensive sequence conservation, defining a monophyletic group among type IV pilins. We further report ComGC solution structures from two naturally competent human pathogens, <jats:italic>Streptococcus sanguinis</jats:italic> (ComGC<jats:sub>SS</jats:sub>) and <jats:italic>Streptococcus pneumoniae</jats:italic> (ComGC<jats:sub>SP</jats:sub>), revealing that this pilin displays extensive structural conservation. Strikingly, ComGC<jats:sub>SS</jats:sub> and ComGC<jats:sub>SP</jats:sub> exhibit a novel type IV pilin fold that is purely helical. Results from homology modeling analyses suggest that the unusual structure of ComGC is compatible with helical filament assembly. Because ComGC displays such a widespread distribution, these results have implications for hundreds of monoderm species.</jats:p>
Chorev DS, Tang H, Rouse SL, et al., 2020, The use of sonicated lipid vesicles for mass spectrometry of membrane protein complexes, NATURE PROTOCOLS, Vol: 15, Pages: 1690-1706, ISSN: 1754-2189
Matthews S, McKenna S, Malito E, et al., 2020, Structure, dynamics and immunogenicity of a catalytically inactive CXC Chemokine-degrading Protease SpyCEP from Streptococcus pyogenes, Computational and Structural Biotechnology Journal, Vol: 18, Pages: 650-660, ISSN: 2001-0370
Over 18 million disease cases and half a million deaths worldwide are estimated to be caused annually by Group A Streptococcus. A vaccine to prevent GAS disease is urgently needed. SpyCEP (Streptococcus pyogenes Cell-Envelope Proteinase) is a surface-exposed serine protease that inactivates chemokines, impairing neutrophil recruitment and bacterial clearance, and has shown promising immunogenicity in preclinical models. Although SpyCEP structure has been partially characterized, a more complete and higher resolution understanding of its antigenic features would be desirable prior to large scale manufacturing. To address these gaps and facilitate development of this globally important vaccine, we performed immunogenicity studies with a safety-engineered SpyCEP mutant, and comprehensively characterized its structure by combining X-ray crystallography, NMR spectroscopy and molecular dynamics simulations. We found that the catalytically-inactive SpyCEP antigen conferred protection similar to wild-type SpyCEP in a mouse infection model. Further, a new higher-resolution crystal structure of the inactive SpyCEP mutant provided new insights into this large chemokine protease comprising nine domains derived from two non-covalently linked fragments. NMR spectroscopy and molecular simulation analyses revealed conformational flexibility that is likely important for optimal substrate recognition and overall function. These combined immunogenicity and structural data demonstrate that the full-length SpyCEP inactive mutant is a strong candidate human vaccine antigen. These findings show how a multi-disciplinary study was used to overcome obstacles in the development of a GAS vaccine, an approach applicable to other future vaccine programs. Moreover, the information provided may also facilitate the structure-based discovery of small-molecule therapeutics targeting SpyCEP protease inhibition.
Murphy P, Xu Y, Rouse SL, et al., 2019, Functional 3D architecture in an intrinsically disordered E3 ligase domain facilitates ubiquitin transfer
<jats:title>Abstract</jats:title><jats:p>Post-translational modification of proteins with ubiquitin represents a widely used mechanism for cellular regulation. Ubiquitin is activated by an E1 enzyme, transferred to an E2 conjugating enzyme and covalently linked to substrates by one of an estimated 600 E3 ligases (1). RING E3 ligases play a pivotal role in selecting substrates and priming the ubiquitin loaded E2 (E2~Ub) for catalysis (2,3). RING E3 RNF4 is a SUMO targeted ubiquitin ligase (4) with important roles in arsenic therapy for cancer (4,5) and in DNA damage responses (6,7). RNF4 has a RING domain and a substrate recognition domain containing multiple SUMO Interaction Motifs (SIM<jats:sc>s</jats:sc>) embedded in a region thought to be intrinsically disordered (8). While molecular details of SUMO recognition by the SIMs (8–10) and RING engagement of ubiquitin loaded E2 (3,11–15) have been determined, the mechanism by which SUMO substrate is delivered to the RING to facilitate ubiquitin transfer is an important question to be answered. Here, we show that the intrinsically disordered substrate-recognition domain of RNF4 maintains the SIMs in a compact global architecture that facilitates SUMO binding, while a highly-basic region positions substrate for nucleophilic attack on RING-bound ubiquitin loaded E2. Contrary to our expectation that the substrate recognition domain of RNF4 was completely disordered, distance measurements using single molecule Fluorescence Resonance Energy Transfer (smFRET) and NMR paramagnetic relaxation enhancement (PRE) revealed that it adopts a defined conformation primed for SUMO interaction. Mutational and biochemical analysis indicated that electrostatic interactions involving the highly basic region linking the substrate recognition and RING domains juxtaposed those regions and mediated substrate ubiquitination. Our results offer insight into a key step in substrate ubiquitination by a membe
Wang Z, Zhao S, Jiang S, et al., 2019, Resonance assignments of N-terminal receiver domain of sigma factor S regulator RssB from Escherichia coli, BIOMOLECULAR NMR ASSIGNMENTS, Vol: 13, Pages: 333-337, ISSN: 1874-2718
Tabib-Salazar A, Mulvenna N, Severinov K, et al., 2019, Xenogeneic regulation of the bacterial transcription machinery, Journal of Molecular Biology, Vol: 431, Pages: 4078-4092, ISSN: 0022-2836
The parasitic life cycle of viruses involves the obligatory subversion of the host's macromolecular processes for efficient viral progeny production. Viruses that infect bacteria, bacteriophages (phages), are no exception and have evolved sophisticated ways to control essential biosynthetic machineries of their bacterial prey to benefit phage development. The xenogeneic regulation of bacterial cell function is a poorly understood area of bacteriology. The activity of the bacterial transcription machinery, the RNA polymerase (RNAP), is often regulated by a variety of mechanisms involving small phage-encoded proteins. In this review, we provide a brief overview of known phage proteins that interact with the bacterial RNAP and compare how two prototypical phages of Escherichia coli, T4 and T7, use small proteins to 'puppeteer' the bacterial RNAP to ensure a successful infection.
Berry J, Gurung I, Anonsen JH, et al., 2019, Global biochemical and structural analysis of the type IV pilus from the Gram-positive bacterium Streptococcus sanguinis, Journal of Biological Chemistry, Vol: 294, Pages: 6796-6808, ISSN: 0021-9258
Type IV pili (Tfp) are functionally versatile filaments, widespread in prokaryotes, that belong to a large class of filamentous nanomachines known as type IV filaments (Tff). Although Tfp have been extensively studied in several Gram-negative pathogens where they function as key virulence factors, many aspects of their biology remain poorly understood. Here, we performed a global biochemical and structural analysis of Tfp in a recently emerged Gram-positive model, Streptococcus sanguinis. In particular, we focused on the five pilins and pilin-like proteins involved in Tfp biology in S. sanguinis. We found that the two major pilins, PilE1 and PilE2, (i) follow widely conserved principles for processing by the prepilin peptidase PilD and for assembly into filaments; (ii) display only one of the post-translational modifications frequently found in pilins, i.e. a methylated N-terminus; (iii) are found in the same hetero-polymeric filaments; and (iv) are not functionally equivalent. The 3D structure of PilE1, solved by NMR, revealed a classical pilin fold with a highly unusual flexible C-terminus. Intriguingly, PilE1 more closely resembles pseudopilins forming shorter Tff than bona fide Tfp-forming major pilins, underlining the evolutionary relatedness among different Tff. Finally, we show that S. sanguinis Tfp contain a low abundance of three additional proteins processed by PilD, the minor pilins PilA, PilB, and PilC. These findings provide the first global biochemical and structural picture of a Gram-positive Tfp and have fundamental implications for our understanding of a widespread class of filamentous nanomachines.
Zhang P, Wang Z, Zhao S, et al., 2019, H-1, C-13 and N-15 NMR assignments of Bacillus subtilis bacteriophage SPO1 protein Gp46, BIOMOLECULAR NMR ASSIGNMENTS, Vol: 13, Pages: 245-247, ISSN: 1874-2718
Miliara X, Tatsuta T, Berry J-L, et al., 2019, Structural determinants of lipid specificity within Ups/PRELI lipid transfer proteins, Nature Communications, Vol: 10, Pages: 1-15, ISSN: 2041-1723
Conserved lipid transfer proteins of the Ups/PRELI family regulate lipid accumulation in mitochondria by shuttling phospholipids in a lipid-specific manner across the intermembrane space. Here, we combine structural analysis, unbiased genetic approaches in yeast and molecular dynamics simulations to unravel determinants of lipid specificity within the conserved Ups/PRELI family. We present structures of human PRELID1–TRIAP1 and PRELID3b–TRIAP1 complexes, which exert lipid transfer activity for phosphatidic acid and phosphatidylserine, respectively. Reverse yeast genetic screens identify critical amino acid exchanges that broaden and swap their lipid specificities. We find that amino acids involved in head group recognition and the hydrophobicity of flexible loops regulate lipid entry into the binding cavity. Molecular dynamics simulations reveal different membrane orientations of PRELID1 and PRELID3b during the stepwise release of lipids. Our experiments thus define the structural determinants of lipid specificity and the dynamics of lipid interactions by Ups/PRELI proteins.
Polo LM, Xu Y, Hornyak P, et al., 2019, Efficient single-strand break repair requires binding to both poly(ADP-Ribose) and DNA by the central BRCT domain of XRCC1, Cell Reports, Vol: 26, Pages: 573-581.e5, ISSN: 2211-1247
XRCC1 accelerates repair of DNA single-strand breaks by acting as a scaffold protein for the recruitment of Polβ, LigIIIα, and end-processing factors, such as PNKP and APTX. XRCC1 itself is recruited to DNA damage through interaction of its central BRCT domain with poly(ADP-ribose) chains generated by PARP1 or PARP2. XRCC1 is believed to interact directly with DNA at sites of damage, but the molecular basis for this interaction within XRCC1 remains unclear. We now show that the central BRCT domain simultaneously mediates interaction of XRCC1 with poly(ADP-ribose) and DNA, through separate and non-overlapping binding sites on opposite faces of the domain. Mutation of residues within the DNA binding site, which includes the site of a common disease-associated human polymorphism, affects DNA binding of this XRCC1 domain in vitro and impairs XRCC1 recruitment and retention at DNA damage and repair of single-strand breaks in vivo.
Andreasen M, Meisl G, Taylor JD, et al., 2019, Physical determinants of amyloid assembly in biofilm formation, mBio, Vol: 10, ISSN: 2150-7511
A wide range of bacterial pathogens have been shown to form biofilms, which significantly increase their resistance to environmental stresses, such as antibiotics, and are thus of central importance in the context of bacterial diseases. One of the major structural components of these bacterial biofilms are amyloid fibrils, yet the mechanism of fibril assembly and its importance for biofilm formation are currently not fully understood. By studying fibril formation in vitro, in a model system of two common but unrelated biofilm-forming proteins, FapC from Pseudomonas fluorescens and CsgA from Escherichia coli, we found that the two proteins have a common aggregation mechanism. In both systems, fibril formation proceeds via nucleated growth of linear fibrils exhibiting similar measured rates of elongation, with negligible fibril self-replication. These similarities between two unrelated systems suggest that convergent evolution plays a key role in tuning the assembly kinetics of functional amyloid fibrils and indicates that only a narrow window of mechanisms and assembly rates allows for successful biofilm formation. Thus, the amyloid assembly reaction is likely to represent a means for controlling biofilm formation, both by the organism and by possible inhibitory drugs.IMPORTANCE Biofilms are generated by bacteria, embedded in the formed extracellular matrix. The biofilm's function is to improve the survival of a bacterial colony through, for example, increased resistance to antibiotics or other environmental stresses. Proteins secreted by the bacteria act as a major structural component of this extracellular matrix, as they self-assemble into highly stable amyloid fibrils, making the biofilm very difficult to degrade by physical and chemical means once formed. By studying the self-assembly mechanism of the fibrils from their monomeric precursors in two unrelated bacteria, our experimental and theoretical approaches shed light on the mechanism of functional amyloid as
Chorev DS, Baker LA, Wu D, et al., 2018, Protein assemblies ejected directly from native membranes yield complexes for mass spectrometry, SCIENCE, Vol: 362, Pages: 829-+, ISSN: 0036-8075
Pakharukova N, McKenna S, Tuittila M, et al., 2018, Archaic and alternative chaperones preserve pilin folding energy by providing incomplete structural information, JOURNAL OF BIOLOGICAL CHEMISTRY, Vol: 293, Pages: 17070-17080, ISSN: 0021-9258
Rouse SL, Matthews SJ, Dueholm MS, 2018, Ecology and biogenesis of functional amyloids in pseudomonas, Journal of Molecular Biology, Vol: 430, Pages: 3685-3695, ISSN: 0022-2836
Functional amyloids can be found in the extracellular matrix produced by many bacteria during biofilm growth. They mediate the initial attachment of bacteria to surfaces and provide stability and functionality to mature biofilms. Efficient amyloid biogenesis requires a highly coordinated system of amyloid subunits, molecular chaperones and transport systems. The functional amyloid of Pseudomonas (Fap) represents such a system. Here, we review the phylogenetic diversification of the Fap system, its potential ecological role and the dedicated machinery required for Fap biogenesis, with a particular focus on the amyloid exporter FapF, the structure of which has been recently resolved. We also present a sequence covariance-based in silico model of the FapC fiber-forming subunit. Finally, we highlight key questions that remain unanswered and we believe deserve further attention by the scientific community.
Darvill N, Blake T, Rouse S, et al., 2018, Structural basis of phosphatidic acid sensing by APH in apicomplexan parasites, Structure, Vol: 26, Pages: 1059-1071.e6, ISSN: 0969-2126
Plasmodium falciparum and Toxoplasma gondii are obligate intracellular parasites that belong to the phylum of Apicomplexa and cause major human diseases. Their access to an intracellular lifestyle is reliant on the coordinated release of proteins from the specialized apical organelles called micronemes and rhoptries. A specific phosphatidic acid effector, the acylated pleckstrin homology domain-containing protein (APH) plays a central role in microneme exocytosis and thus is essential for motility, cell entry, and egress. TgAPH is acylated on the surface of the micronemes and recruited to phosphatidic acid (PA)-enriched membranes. Here, we dissect the atomic details of APH PA-sensing hub and its functional interaction with phospholipid membranes. We unravel the key determinant of PA recognition for the first time and show that APH inserts into and clusters multiple phosphate head-groups at the bilayer binding surface.
Rouse S, Stylianou F, wu G, et al., 2018, The FapF amyloid secretion transporter possesses an atypical asymmetric coiled coil, Journal of Molecular Biology, Vol: 430, Pages: 3863-3871, ISSN: 0022-2836
Gram-negative bacteria possess specialized biogenesis machineries that facilitate the export of amyloid subunits, the fibers of which are key components of their biofilm matrix. The secretion of bacterial functional amyloid requires a specialized outer-membrane protein channel through which unfolded amyloid substrates are translocated. We previously reported the crystal structure of the membrane-spanning domain of the amyloid subunit transporter FapF from Pseudomonas. However, the structure of the periplasmic domain, which is essential for amyloid transport, is yet to be determined. Here, we present the crystal structure of the N-terminal periplasmic domain at 1.8-Å resolution. This domain forms a novel asymmetric trimeric coiled coil that possesses a single buried tyrosine residue as well as an extensive hydrogen-bonding network within a glutamine layer. This new structural insight allows us to understand this newly described functional amyloid secretion system in greater detail.
Liu B, Wang Z, Lan L, et al., 2018, A rapid colorimetric method to visualize protein interactions, Chemistry - A European Journal, Vol: 24, Pages: 6727-6731, ISSN: 0947-6539
As key molecules in most biological pathways, proteins physically contact one or more biomolecules in a highly specific manner. Several driving forces (i.e., electrostatic and hydrophobic) facilitate such interactions and a variety of methods have been developed to monitor these processes both in vivo and in vitro. In this work, a new method is reported for the detection of protein interactions by visualizing a color change of a cyanine compound, a supramolecule complex of 3,3-di-(3-sulfopropyl)-4,5,4',5'-dibenzo-9-methyl-thiacarbocyanine triethylammonium salt (MTC). Nuclear magnetic resonance (NMR) studies suggest that the hydrophobic nature of the protein surfaces drives MTC into different types of aggregates with distinct colors. When proteins interact with other biomolecules, the hydrophobic surface of the complex differs, resulting in a shift in the form of MTC aggregation, which results in a color change. As a result, this in vitro method has the potential to become a rapid tool for the confirmation of protein-biomolecule interactions, without the requirements for sophisticated instrumentation or approaches.
Tabib-Salazar A, Liu B, Declan B, et al., 2018, T7 phage factor required for managing RpoS in Escherichia coli, Proceedings of the National Academy of Sciences, Vol: 115, Pages: E5353-E5362, ISSN: 0027-8424
T7 development in Escherichia coli requires the inhibition of the housekeepingform of the bacterial RNA polymerase (RNAP), Eσ70, by two T7 proteins: Gp2and Gp5.7. While the biological role of Gp2 is well understood, that of Gp5.7remains to be fully deciphered. Here, we present results from functional andstructural analyses to reveal that Gp5.7 primarily serves to inhibit EσS, thepredominant form of the RNAP in the stationary phase of growth, whichaccumulates in exponentially growing E. coli as a consequence of buildup ofguanosine pentaphosphate ((p)ppGpp) during T7 development. We furtherdemonstrate a requirement of Gp5.7 for T7 development in E. coli cells in thestationary phase of growth. Our finding represents a paradigm for how somelytic phages have evolved distinct mechanisms to inhibit the bacterialtranscription machinery to facilitate phage development in bacteria in theexponential and stationary phases of growth.
Gatta AT, Sauerwein AC, Zhuravleva A, et al., 2018, Structural insights into a StART-like domain in Lam4 and its interaction with sterol ligands, BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS, Vol: 495, Pages: 2270-2274, ISSN: 0006-291X
rouse S, hawthorne, berry, et al., 2017, A new class of hybrid secretion system is employed in Pseudomonas amyloid biogenesis, Nature Communications, Vol: 8, ISSN: 2041-1723
Gram-negative bacteria possess specialised biogenesis machineries that facilitate the export of amyloid subunits for construction of a biofilm matrix. The secretion of bacterial functional amyloid requires a bespoke outer-membrane protein channel through which unfolded amyloid substrates are translocated. Here, we combine X-ray crystallography, native mass spectrometry, single-channel electrical recording, molecular simulations and circular dichroism measurements to provide high-resolution structural insight into the functional amyloid transporter from Pseudomonas, FapF. FapF forms a trimer of gated β-barrel channels in which opening is regulated by a helical plug connected to an extended coil-coiled platform spanning the bacterial periplasm. Although FapF represents a unique type of secretion system, it shares mechanistic features with a diverse range of peptide translocation systems. Our findings highlight alternative strategies for handling and export of amyloid protein sequences.
Otzen DE, Vad BS, Dueholm MS, et al., 2017, Self-organizing amyloid in bacteria, 19th IUPAB Congress / 11th EBSA Congress, Publisher: SPRINGER, Pages: S341-S341, ISSN: 0175-7571
Otzen DE, Vad BS, Dueholm MS, et al., 2017, Self-organizing amyloid in bacteria, 19th IUPAB Congress / 11th EBSA Congress, Publisher: SPRINGER, Pages: S98-S98, ISSN: 0175-7571
Tabib-Salazar A, Liu B, Shadrin A, et al., 2017, Full shut-off of Escherichia coli RNA-polymerase by T7 phage requires a small phage-encoded DNA-binding protein, Nucleic Acids Research, Vol: 45, Pages: 7697-7707, ISSN: 1362-4962
Infection of Escherichia coli by the T7 phage leads to rapid and selective inhibition of the bacterial RNA polymerase (RNAP) by the 7 kDa T7 protein Gp2. We describe the identification and functional and structural characterisation of a novel 7 kDa T7 protein, Gp5.7, which adopts a winged helix-turn-helix-like structure and specifically represses transcription initiation from host RNAP-dependent promoters on the phage genome via a mechanism that involves interaction with DNA and the bacterial RNAP. Whereas Gp2 is indispensable for T7 growth in E. coli, we show that Gp5.7 is required for optimal infection outcome. Our findings provide novel insights into how phages fine-tune the activity of the host transcription machinery to ensure both successful and efficient phage progeny development.
Jia Y, Benjamin S, Liu Q, et al., 2017, "Toxoplasma gondii immune mapped protein 1 is anchored to the inner leaflet of the plasma membrane and adopts a novel protein fold" (vol 1865, pg 208, 2017), BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS, Vol: 1865, Pages: 631-631, ISSN: 1570-9639
Wang S, Lin Y, Todorova N, et al., 2017, Facet-dependent interactions of islet amyloid polypeptide with gold nanoparti-cles: implications for fibril formation and peptide-induced lipid membrane dis-ruption, Chemistry of Materials, Vol: 29, ISSN: 1520-5002
A comprehensive understanding of the mechanisms of interaction between proteins or peptides and nanomaterials is crucial for the development of nanomaterial-based diagnos-tics and therapeutics. In this work, we systematically explored the interactions between citrate-capped gold nanoparticles (AuNPs) and islet amyloid polypeptide (IAPP), a 37-amino acid peptide hormone co-secreted with insulin from the pancreatic islet. We uti-lized diffusion-ordered spectroscopy, isothermal titration calorimetry, localized surface plasmon resonance spectroscopy, gel electrophoresis, atomic force microscopy, transmis-sion electron microscopy (TEM), and molecular dynamics (MD) simulations to systemati-cally elucidate the underlying mechanism of the IAPP−AuNP interactions. Because of the presence of a metal-binding sequence motif in the hydrophilic peptide domain, IAPP strongly interacts with the Au surface in both the monomeric and fibrillar states. Circular dichroism showed that AuNPs triggered the IAPP conformational transition from random coil to ordered structures (α-helix and β-sheet), and TEM imaging suggested the accelera-tion of IAPP fibrillation in the presence of AuNPs. MD simulations revealed that the IAPP−AuNP interactions were initiated by the N-terminal domain (IAPP residues 1−19), which subsequently induced a facet-dependent conformational change in IAPP. On a Au(111) surface, IAPP was unfolded and adsorbed directly onto the Au surface, while for the Au(100) surface, it interacted predominantly with the citrate adlayer and retained some helical conformation. The observed affinity of AuNPs for IAPP was further applied to reduce the level of peptide-induced lipid membrane disruption.
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