The Experts below are selected from a list of 1494 Experts worldwide ranked by ideXlab platform

Jean Chmielewski - One of the best experts on this subject based on the ideXlab platform.

  • Antibacterial activity and therapeutic efficacy of Fl-P(R)P(R)P(L)-5, a cationic amphiphilic Polyproline Helix, in a mouse model of staphylococcal skin infection.
    Drug design development and therapy, 2015
    Co-Authors: Shankar Thangamani, Jean Chmielewski, Manish Nepal, Mohamed N. Seleem
    Abstract:

    The antibacterial activities and therapeutic efficacy of the cationic, unnatural proline-rich peptide Fl-P(R)P(R)P(L)-5 were evaluated against multidrug-resistant Staphylococcus aureus in a mouse model of skin infection. Fl-P(R)P(R)P(L)-5 showed potent activity against all clinical isolates of S. aureus tested, including methicillin- and vancomycin-resistant S. aureus (MRSA and VRSA, respectively). Fl-P(R)P(R)P(L)-5 was also superior in clearing established in vitro biofilms of S. aureus and Staphylococcus epidermidis, compared with the established antimicrobials mupirocin and vancomycin. Additionally, topical treatment of an MRSA-infected wound with Fl-P(R)P(R)P(L)-5 enhanced wound closure and significantly reduced bacterial load. Finally, 0.5% Fl-P(R)P(R)P(L)-5 significantly reduced the levels of the inflammatory cytokines tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1 beta (IL-1β) in wounds induced by MRSA skin infection. In conclusion, the results of this study suggest the potential application of Fl-P(R)P(R)P(L)-5 in the treatment of staphylococcal skin infections.

  • Targeting intracellular bacteria with an extended cationic amphiphilic Polyproline Helix
    Organic & biomolecular chemistry, 2015
    Co-Authors: Manish Nepal, Shankar Thangamani, Mohamed N. Seleem, Jean Chmielewski
    Abstract:

    An extended cationic and amphiphilic Polyproline Helix (CAPH) is described with a dual mode of action: effective cell penetration of human macrophages, and potent antimicrobial activity in vitro against both Gram-positive and negative pathogens, including Acinetobacter baumannii, Escherichia coli O157 and Bacillus anthracis. This dual action was successfully combined to clear pathogenic bacteria (Brucella and Salmonella) residing within macrophages.

  • Mitochondrial targeting of a cationic amphiphilic Polyproline Helix.
    Bioorganic & medicinal chemistry letters, 2011
    Co-Authors: Deanna Kalafut, Tiffani N. Anderson, Jean Chmielewski
    Abstract:

    The development of cell penetrating peptides (CPPs) for the cellular delivery of attached cargo is an area of growing interest. Many CPPs, however, are found trapped within endosomes, thereby limiting their use as drug delivery agents with sub-cellular applications. Herein, we detail the properties of a highly efficient class of CPPs, cationic amphiphilic Polyproline helices (CAPHs), that are found localized to the mitochondria by direct transport into cells.

  • cationic amphiphilic Polyproline Helix p11lrr targets intracellular mitochondria
    Journal of Controlled Release, 2010
    Co-Authors: Iris Geisler, Jean Chmielewski, Jixin Cheng
    Abstract:

    We demonstrate that P11LRR, a recently developed amphiphilic Polyproline, cell penetrating agent, is able to locate inside the mitochondria of various cell lines when administrated at high concentrations. Mitochondrial targeting was verified by confocal fluorescence co-localization of P11LRR-fluorescein with Mitotracker Red. Elimination of mitochondrial membrane potential dramatically inhibits the localization of P11LRR to mitochondria. Concentration-dependency experiments suggest that cellular internalization of P11LRR occurs via two different pathways: endocytosis and direct transport. Results indicate that the latter pathway predominates at high concentrations of P11LRR, resulting in localization of the agent to the mitochondria. The membrane translocation pathway was further confirmed by two endocytosis inhibitors, cytochalasin D and phenylarsine oxide, and by modulation of plasma membrane potential. The potential of using P11LRR as a mitochondrial drug delivery vector was demonstrated through the delivery of a covalently linked small antioxidant, dimethyltyrosine (Dmt), which allowed for the reduction of chemically induced reactive oxygen species within the mitochondria.

  • Probing length effects and mechanism of cell penetrating agents mounted on a Polyproline Helix scaffold.
    Bioorganic & medicinal chemistry letters, 2007
    Co-Authors: Iris Geisler, Jean Chmielewski
    Abstract:

    Cell penetrating peptides (CPP) displaying a type II Polyproline Helix backbone of different length and amphiphilic character were synthesized and their cellular uptake was compared. The longer CPP sequence, P14LRR, displayed a 7- to 12-fold higher uptake in MCF-7 cells as compared to its shorter counterpart, P11LRR, and a 35-fold higher uptake as compared to Tatp. These results demonstrate that an increased number of cationic and hydrophobic residues can strongly influence the extent of cellular internalization. Mechanistic investigations suggest internalization via a receptor independent endocytotic pathway with these agents.

Neal J. Zondlo - One of the best experts on this subject based on the ideXlab platform.

  • An Inherent Structural Difference Between Serine and Threonine Phosphorylation: Phosphothreonine Prefers an Ordered, Compact, Cyclic Conformation
    2020
    Co-Authors: Anil K. Pandey, Himal K. Ganguly, Sudipta Kumar Sinha, Kelly E. Daniels, Glenn P. A. Yap, Sandeep Patel, Neal J. Zondlo
    Abstract:

    Phosphorylation and dephosphorylation of proteins by kinases and phosphatases are central to cellular responses and function. The structural effects of serine and threonine phosphorylation were examined in peptides and in proteins, by circular dichroism, NMR spectroscopy, bioinformatics analysis of the PDB, small-molecule X-ray crystallography, and computational investigations. Phosphorylation of both serine and threonine residues induces substantial conformational restriction in their physiologically more important dianionic forms. Threonine exhibits a particularly strong disorder-to-order transition upon phosphorylation, with dianionic phosphothreonine preferentially adopting a cyclic conformation with restricted{phi} ({phi} [~] -60{degrees}) stabilized by three noncovalent interactions: a strong intraresidue phosphate-amide hydrogen bond, an n[->]{pi}* interaction between consecutive carbonyls, and an n[->]{sigma}* interaction between the phosphate O{gamma} lone pair and the antibonding orbital of C-H{beta} that restricts the{chi} 2 side chain conformation. Proline is unique among the canonical amino acids for its covalent cyclization on the backbone. Phosphothreonine can mimic prolines backbone cyclization via noncovalent interactions. The preferred torsions of dianionic phosphothreonine are{phi} ,{psi} = Polyproline Helix or -Helix ({phi} [~] -60{degrees});{chi} 1 = g-;{chi} 2 = eclipsed C-H/O-P bonds. This structural signature is observed in diverse proteins, including the activation loops of protein kinases and protein-protein interactions. In total, these results suggest a structural basis for the differential use and evolution of threonine versus serine phosphorylation sites in proteins, with serine phosphorylation typically inducing smaller, rheostat-like changes, versus threonine phosphorylation promoting larger, step function-like switches, in proteins.

  • Perfluoro-tert-butyl Homoserine Is a Helix-Promoting, Highly Fluorinated, NMR-Sensitive Aliphatic Amino Acid: Detection of the Estrogen Receptor·Coactivator Protein–Protein Interaction by 19F NMR
    2017
    Co-Authors: Caitlin M. Tressler, Neal J. Zondlo
    Abstract:

    Highly fluorinated amino acids can stabilize proteins and complexes with proteins, via enhanced hydrophobicity, and provide novel methods for identification of specific molecular events in complex solutions, via selective detection by 19F NMR and the absence of native 19F signals in biological contexts. However, the potential applications of 19F NMR in probing biological processes are limited both by the strong propensities of most highly fluorinated amino acids for the extended conformation and by the relatively modest sensitivity of NMR spectroscopy, which typically constrains measurements to mid-micromolar concentrations. Herein, we demonstrate that perfluoro-tert-butyl homoserine exhibits a propensity for compact conformations, including α-Helix and Polyproline Helix (PPII), that is similar to that of methionine. Perfluoro-tert-butyl homoserine has nine equivalent fluorines that do not couple to any other nuclei, resulting in a sharp singlet that can be sensitively detected rapidly at low micromolar concentrations. Perfluoro-tert-butyl homoserine was incorporated at sites of leucine residues within the α-helical LXXLL short linear motif of estrogen receptor (ER) coactivator peptides. A peptide containing perfluoro-tert-butyl homoserine at position i + 3 of the ER coactivator LXXLL motif exhibited a Kd of 2.2 μM for the estradiol-bound estrogen receptor, similar to that of the native ligand. 19F NMR spectroscopy demonstrated the sensitive detection (5 μM concentration, 128 scans) of binding of the peptide to the ER and of inhibition of protein–protein interaction by the native ligand or by the ER antagonist tamoxifen. These results suggest diverse potential applications of perfluoro-tert-butyl homoserine in probing protein function and protein–protein interfaces in complex solutions

  • Tunable Control of Polyproline Helix (PPII) Structure via Aromatic Electronic Effects: An Electronic Switch of Polyproline Helix
    2016
    Co-Authors: Anil K. P, Christina R. Forbes, Krista M. Thomas, Neal J. Zondlo
    Abstract:

    ABSTRACT: Aromatic rings exhibit defined interactions via the unique aromatic π face. Aromatic amino acids interact favorably with proline residues via both the hydrophobic effect and aromatic−proline interactions, C−H/π interactions between the aromatic π face and proline ring C−H bonds. The canonical aromatic amino acids Trp, Tyr, and Phe strongly disfavor a Polyproline Helix (PPII) when they are present in proline-rich sequences because of the large populations of cis amide bonds induced by favorable aromatic−proline interactions (aromatic−cis-proline and proline−cis-proline−aromatic interactions). We demonstrate the ability to tune Polyproline Helix conformation and cis−trans isomerism in proline-rich sequences using aromatic electronic effects. Electron-rich aromatic residues strongly disfavor Polyproline Helix and exhibit large populations of cis amide bonds, while electron-poor aromatic residues exhibit small populations of cis amide bonds and favor Polyproline Helix. 4-Aminophenylalanine is a pH-dependent electronic switch of Polyproline Helix, with cis amide bonds favored as the electron-donating amine, but trans amide bonds and Polyproline Helix preferred as the electron-withdrawing ammonium. Peptides with block proline−aromatic PPXPPXPPXPP sequences exhibited electronically switchable pH-dependen

  • OGlcNAcylation and Phosphorylation Have Opposing Structural Effects in tau: Phosphothreonine Induces Particular Conformational Order
    2016
    Co-Authors: Michael Brister, Anil K. P, Agata A. Bielska, Neal J. Zondlo
    Abstract:

    dynamic intracellular protein post-translational modifications that frequently are alternatively observed on the same serine and threonine residues. Phosphorylation and OGlcNAcylation commonly occur in natively disordered regions of proteins, and often have opposing functional effects. In the microtubule-associated protein tau, hyperphosphorylation is associated with protein misfolding and aggregation as the neurofibrillary tangles of Alzheimer’s disease, whereas OGlcNAcylation stabilizes the soluble form of tau. A series of peptides derived from the proline-rich domain (residues 174−251) of tau was synthesized, with free Ser/Thr hydroxyls, phosphorylated Ser/Thr (pSer/pThr), OGlcNAcylated Ser/Thr, and diethylphosphorylated Ser/Thr. Phosphorylation and OGlcNAcylation were found by CD and NMR to have opposing structural effects on Polyproline Helix (PPII) formation, with phosphorylation favoring PPII, OGlcNAcylation opposing PPII, and the free hydroxyls intermediate in structure, and with phosphorylation structural effects greater than OGlcNAcylation. For tau196−209, phosphorylation and OGlcNAcylation had similar structural effects, opposing a nascent α-Helix. Phosphomimic Glu exhibited PPII-favoring structural effects. Structural changes due to Thr phosphorylation were greater than those of Ser phosphorylation or Glu, with particular conformational restriction as the dianion, with mean 3JαN = 3.5 Hz (pThr) versus 5.4 Hz (pSer), compared to 7.2, 6.8, and 6.2 Hz for Thr, Ser, and Glu, respectively, values that correlate with the backbone torsion angle ϕ. Dianionic phosphothreonine induced strong phosphothreonine amide protection and downfield amide chemical shifts (δmean = 9.63 ppm), consistent with formation of a stable phosphate-amide hydrogen bond. These data suggest potentially greater structural importance of threonine phosphorylation than serine phosphorylation due to larger induced structural effects

  • (2S,4R)- and (2S,4S)‑Perfluoro-tert-butyl 4‑Hydroxyproline: Two Conformationally Distinct Proline Amino Acids for Sensitive Application in 19F NMR
    2016
    Co-Authors: Caitlin M. Tressler, Neal J. Zondlo
    Abstract:

    amino acids) in 2−5 steps. The key step of each synthesis was a Mitsunobu reaction with perfluoro-tert-butanol, which incorporated a perfluoro-tert-butyl group, with nine chemically equivalent fluorines. Both amino acids were incorporated in model α-helical and Polyproline Helix peptides. Each amino acid exhibited distinct conformational preferences, with (2S,4R)-perfluoro-tert-butyl 4-hydroxyproline promoting Polyproline Helix. Peptides containing these amino acids were sensitively detected by 19F NMR, suggesting their use in probes and medicinal chemistry. Fluorinated amino acids have unique properties, due to thehydrophobicity and electronegativity of fluorine and the magnetic properties of the sensitive spin-1/2 19F nucleus.1−10 The special nature of fluorine has led to broad interest in the incorporation of fluorinated amino acids in small molecules, peptides, and proteins, for applications in medicinal chemistry, in the design of stabilized proteins, and in NMR and MRI approaches to protein detection and imaging.11−34 Fluorinated amino acids allow the specific, quantitative detection o

Jeetain Mittal - One of the best experts on this subject based on the ideXlab platform.

  • computational modeling highlights the role of the disordered formin homology 1 domain in profilin actin transfer
    FEBS Letters, 2018
    Co-Authors: Brandon Gregory Horan, Gül H Zerze, Dimitrios Vavylonis, Youngchan Kim, Jeetain Mittal
    Abstract:

    Formins accelerate actin polymerization, assumed to occur through flexible Formin Homology 1 (FH1) domain-mediated transfer of profilin-actin to the barbed end. To study FH1 properties and address sequence effects, including varying length/distribution of profilin-binding proline-rich motifs, we performed all-atom simulations of a set of representative FH1 domains of formins: mouse mDia1 and mDia2, budding yeast Bni1 and Bnr1, and fission yeast Cdc12, For3, and Fus1. We find FH1 has flexible regions between high-propensity Polyproline Helix regions. A coarse-grained model retaining sequence specificity, assuming rigid Polyproline segments, describes their size. Multiple bound profilins or profilin-actin complexes expand mDia1-FH1, which may be important in cells. Simulations of the barbed end bound to Bni1-FH1-FH2 dimer show that the leading FH1 can better transfer profilin or profilin-actin, with decreasing probability as the distance from FH2 increases.

  • computational modeling highlights disordered formin homology 1 domain s role in profilin actin transfer
    bioRxiv, 2018
    Co-Authors: Brandon Gregory Horan, Gül H Zerze, Dimitrios Vavylonis, Youngchan Kim, Jeetain Mittal
    Abstract:

    Formins accelerate actin polymerization, assumed to occur through flexible FH1 domain mediated transfer of profilin-actin to the barbed end. To study FH1 properties and address sequence effects including varying length/distribution of profilin-binding proline-rich motifs, we performed all-atom simulations of mouse mDia1, mDia2; budding yeast Bni1, Bnr1; fission yeast Cdc12, For3, and Fus1 FH1s. We find FH1 has flexible regions between high propensity Polyproline Helix regions. A coarse-grained model retaining sequence-specificity, assuming rigid Polyproline segments, describes their size. Multiple profilins and profilin-actin complexes can simultaneously bind, expanding mDia1-FH1, which may be important in cells. Simulations of the barbed end bound to Bni1-FH1-FH2 dimer show the leading FH1 can better transfer profilin or profilin-actin, having decreasing probability with increasing distance from FH2.

  • Dataset for: Computational modeling highlights disordered Formin Homology 1 domain's role in profilin-actin transfer
    2018
    Co-Authors: Brandon Gregory Horan, Gül H Zerze, Young C. Kim, Dimitrios Vavylonis, Jeetain Mittal
    Abstract:

    Formins accelerate actin polymerization, assumed to occur through flexible FH1 domain mediated transfer of profilin-actin to the barbed end. To study FH1 properties and address sequence effects including varying length/distribution of profilin-binding proline-rich motifs, we performed all-atom simulations of mouse mDia1, mDia2; budding yeast Bni1, Bnr1; fission yeast Cdc12, For3, and Fus1 FH1s. We find FH1 has flexible regions between high propensity Polyproline Helix regions. A coarse-grained model retaining sequence-specificity, assuming rigid Polyproline segments, describes their size. Multiple bound profilins or profilin-actin complexes expand mDia1-FH1, which may be important in cells. Simulations of the barbed end bound to Bni1-FH1-FH2 dimer show the leading FH1 can better transfer profilin or profilin-actin, having decreasing probability with increasing distance from FH2

Brandon Gregory Horan - One of the best experts on this subject based on the ideXlab platform.

  • computational modeling highlights the role of the disordered formin homology 1 domain in profilin actin transfer
    FEBS Letters, 2018
    Co-Authors: Brandon Gregory Horan, Gül H Zerze, Dimitrios Vavylonis, Youngchan Kim, Jeetain Mittal
    Abstract:

    Formins accelerate actin polymerization, assumed to occur through flexible Formin Homology 1 (FH1) domain-mediated transfer of profilin-actin to the barbed end. To study FH1 properties and address sequence effects, including varying length/distribution of profilin-binding proline-rich motifs, we performed all-atom simulations of a set of representative FH1 domains of formins: mouse mDia1 and mDia2, budding yeast Bni1 and Bnr1, and fission yeast Cdc12, For3, and Fus1. We find FH1 has flexible regions between high-propensity Polyproline Helix regions. A coarse-grained model retaining sequence specificity, assuming rigid Polyproline segments, describes their size. Multiple bound profilins or profilin-actin complexes expand mDia1-FH1, which may be important in cells. Simulations of the barbed end bound to Bni1-FH1-FH2 dimer show that the leading FH1 can better transfer profilin or profilin-actin, with decreasing probability as the distance from FH2 increases.

  • computational modeling highlights disordered formin homology 1 domain s role in profilin actin transfer
    bioRxiv, 2018
    Co-Authors: Brandon Gregory Horan, Gül H Zerze, Dimitrios Vavylonis, Youngchan Kim, Jeetain Mittal
    Abstract:

    Formins accelerate actin polymerization, assumed to occur through flexible FH1 domain mediated transfer of profilin-actin to the barbed end. To study FH1 properties and address sequence effects including varying length/distribution of profilin-binding proline-rich motifs, we performed all-atom simulations of mouse mDia1, mDia2; budding yeast Bni1, Bnr1; fission yeast Cdc12, For3, and Fus1 FH1s. We find FH1 has flexible regions between high propensity Polyproline Helix regions. A coarse-grained model retaining sequence-specificity, assuming rigid Polyproline segments, describes their size. Multiple profilins and profilin-actin complexes can simultaneously bind, expanding mDia1-FH1, which may be important in cells. Simulations of the barbed end bound to Bni1-FH1-FH2 dimer show the leading FH1 can better transfer profilin or profilin-actin, having decreasing probability with increasing distance from FH2.

  • Dataset for: Computational modeling highlights disordered Formin Homology 1 domain's role in profilin-actin transfer
    2018
    Co-Authors: Brandon Gregory Horan, Gül H Zerze, Young C. Kim, Dimitrios Vavylonis, Jeetain Mittal
    Abstract:

    Formins accelerate actin polymerization, assumed to occur through flexible FH1 domain mediated transfer of profilin-actin to the barbed end. To study FH1 properties and address sequence effects including varying length/distribution of profilin-binding proline-rich motifs, we performed all-atom simulations of mouse mDia1, mDia2; budding yeast Bni1, Bnr1; fission yeast Cdc12, For3, and Fus1 FH1s. We find FH1 has flexible regions between high propensity Polyproline Helix regions. A coarse-grained model retaining sequence-specificity, assuming rigid Polyproline segments, describes their size. Multiple bound profilins or profilin-actin complexes expand mDia1-FH1, which may be important in cells. Simulations of the barbed end bound to Bni1-FH1-FH2 dimer show the leading FH1 can better transfer profilin or profilin-actin, having decreasing probability with increasing distance from FH2

Jean-christophe Gelly - One of the best experts on this subject based on the ideXlab platform.

  • PolyprOnline: Polyproline Helix II and secondary structure assignment database.
    Database : the journal of biological databases and curation, 2014
    Co-Authors: Romain Chebrek, Sylvain Leonard, Alexandre G. De Brevern, Jean-christophe Gelly
    Abstract:

    The Polyproline Helix type II (PPII) is a regular protein secondary structure with remarkable features. Many studies have highlighted different crucial biological roles supported by this local conformation, e.g. in the interactions between biological macromolecules. Although PPII is less frequently present than regular secondary structures such as canonical alpha helices and beta strands, it corresponds to 3–10% of residues. Up to now, PPII is not assigned by most popular assignment tools, and therefore, remains insufficiently studied. PolyprOnline database is, therefore, dedicated to PPII structure assignment and analysis to facilitate the study of PPII structure and functional roles. This database is freely accessible from www.dsimb.inserm.fr/dsimb_tools/Polyproline.