Cytotoxic Natural Products Isolated from Cryptogramma crispa (L.) R. Br

Parsley fern, Cryptogramma crispa, is a common fern in arctic-alpine regions, and even though this species has been known since ancient times and has been presumed to cause the poisoning of horses, its natural products have not previously been investigated. Here, we characterise 15 natural products isolated from the aerial parts of Cryptogramma crispa, including the previously undescribed compound 3-malonyl pteroside D. The structure determinations were based on several advanced 1D and 2D NMR spectroscopic techniques, Circular Dichroism spectroscopy and high-resolution mass spectrometry. The pteroside derivatives exhibited selective moderate cytotoxic activity against the acute myeloid leukaemia MOLM13 cell line and no cytotoxicity against the normal heart and kidney cell lines, suggesting that their potential anticancer effect should be further investigated.

Acylated Flavone O-Glucuronides from the Aerial Parts of Nepeta curviflora

Nepeta curviflora Boiss. (Syrian catnip) is native to the Middle East. This medicinal plant is commonly used against nervous disorders, rheumatic pains, and high blood pressure. Herbal infusions prepared from various Nepeta spp. are extensively consumed as functional food. However, limited information has been known about the phenolic constituents of Syrian catnip. In this study, two acylated flavone 7-O-glucuronides, apigenin 7-O-(2″-O-(2‴-(E-caffeoyl)-β-glucuronopyranosyl)-β-glucuronopyranoside) (1) and luteolin 7-O-(2″-O-(2‴-(E-caffeoyl)-β-glucuronopyranosyl)-β-glucuronopyranoside) (2), along with the known phenolic compounds rosmarinic acid, caffeic acid, apigenin, and apigenin 7-O-β-glucopyranoside were isolated from the aerial parts of N. curviflora. The characterizations of these compounds were based on high-resolution mass spectrometry, UV, and extensive use of multidimensional NMR spectroscopy. The new compounds (1 and 2) were identified in the unmodified state and as dimethylesters.

Cytotoxic saponins and other natural products from flowering tops of Narthecium ossifragum L

For more than four centuries, the intake of Narthecium ossifragum has been associated with poisoning in domesticated animals. Saponins occurring in flowering tops of the plant are considered to cause kidney damage in calves. At present, there are more than 30 papers on the saponins of N. ossifragum in the literature, although the structures of these compounds have hitherto not been determined. Here, we identify the saponins of N. ossifragum as sarsasapogenin, sarsasapogenin-3-O-β-galactopyranoside, sarsasapogenin-3-O-(2'-O-β-glucopyranosyl-β-galactopyranoside) and sarsasapogenin-3-O-(2'-O-β-glucopyranosyl-3'-O-α-arabinopyranosyl-β-galactopyranoside). Moreover, six aromatic natural products were isolated and characterized from the methanolic extract from flowers of N. ossifragum. Five of these aromatic compounds, chrysoeriol 6-C-β-arabinofuranoside-8-C-β-glucopyranoside, chrysoeriol 6-C-β-arabinopyranosyl-8-C-β-glucopyranoside, chrysoeriol 6-C-β-xylopyranosyl-8-C-β-galactopyranoside, chrysoeriol 6-C-β-galactopyranosyl-8-C-β-glucopyranoside and chrysoeriol 6-C-β-glucopyranosyl-8-C-β-galactopyranoside are undescribed. All compounds were tested for cytotoxicity in mammalian cell lines derived from the heart, kidney, and haematological tissues. The saponins exhibited cytotoxicity in the micromolar range, with proportionally increasing cytotoxicity with increasing number of glycosyl substituents. The most potent compound was the main saponin sarsasapogenin-3-O-(2'-O-β-glucopyranosyl-3'-O-α-arabinopyranosyl-β-galactopyranoside), which produced cell death at concentrations below 3-4 μM in all three cell lines tested. This indicates that the saponins are the toxicants mainly responsible for kidney damage observed in cattle after ingestion of N. ossifragum. Our findings also pave the way for analysis of individual compounds isolated during the biopsies of intoxicated animals.

A novel poly-oxygenated flavone glucoside from aerial parts of the Brazilian plant Neoglaziovia variegata (Bromeliaceae)

Neoglaziovia variegata is endemic to northeastern Brazil. The drought resistant plant produces edible fruits and is used as a fibre plant by rural communities in the Caatinga region where a variety of products are made from the white, soft and flexible fibres. Extracts of N. variegata have been reported to be of low toxicity and to exhibit antinociceptive effect, photoprotective potential, antioxidant effect, gastroprotective effects and antibacterial effect against both Gram-positive and Gram-negative bacteria, however, the chemical constituents of this species are mainly unknown. The novel poly-oxygenated flavone glucoside 5,6,7,4'-tetrahydroxy-3',5'-dimethoxy-flavone 7-O-β-glucopyranoside in addition to the rare poly-oxygenated flavone 5,4'-dihydroxy-6,7,3'-trimethoxyflavone 4'-O-β-glucopyranoside and the flavonol quercetin 3-O-(6''-rhamnopyranosyl-β-glucopyranoside) have been characterised from the leaves of N. variegata. 5,6,7,4'-tetrahydroxy-3',5'-dimethoxy-flavone, which comprises the core structure of the novel compound, is a new flavonoid aglycone in nature. The structure determinations were based on extensive use of 2D NMR spectroscopic techniques and high-resolution mass spectrometry. Both substances exhibited toxicity towards MOLM-13 acute myeloid leukaemia cells.

Proteolysis of mature HIV-1 p6 Gag protein by the insulin-degrading enzyme (IDE) regulates virus replication in an Env-dependent manner

There is a significantly higher risk for type II diabetes in HIV-1 carriers, albeit the molecular mechanism for this HIV-related pathology remains enigmatic. The 52 amino acid HIV-1 p6 Gag protein is synthesized as the C-terminal part of the Gag polyprotein Pr55. In this context, p6 promotes virus release by its two late (L-) domains, and facilitates the incorporation of the viral accessory protein Vpr. However, the function of p6 in its mature form, after proteolytic release from Gag, has not been investigated yet. We found that the mature p6 represents the first known viral substrate of the ubiquitously expressed cytosolic metalloendopeptidase insulin-degrading enzyme (IDE). IDE is sufficient and required for degradation of p6, and p6 is approximately 100-fold more efficiently degraded by IDE than its eponymous substrate insulin. This observation appears to be specific for HIV-1, as p6 proteins from HIV-2 and simian immunodeficiency virus, as well as the 51 amino acid p9 from equine infectious anaemia virus were insensitive to IDE degradation. The amount of virus-associated p6, as well as the efficiency of release and maturation of progeny viruses does not depend on the presence of IDE in the host cells, as it was shown by CRISPR/Cas9 edited IDE KO cells. However, HIV-1 mutants harboring IDE-insensitive p6 variants exhibit reduced virus replication capacity, a phenomenon that seems to depend on the presence of an X4-tropic Env. Furthermore, competing for IDE by exogenous insulin or inhibiting IDE by the highly specific inhibitor 6bK, also reduced virus replication. This effect could be specifically attributed to IDE since replication of HIV-1 variants coding for an IDE-insensitive p6 were inert towards IDE-inhibition. Our cumulative data support a model in which removal of p6 during viral entry is important for virus replication, at least in the case of X4 tropic HIV-1.

Toxic aromatic compounds from fruits of Narthecium ossifragum L

The intake of Narthecium ossifragum, commonly known as bog asphodel, has been associated with toxic effects observed in sheep for centuries. Although the plant has been studied for five centuries little is known about its chemical constituents. Six previously undescribed natural products, naringenin(3 → 6″)luteolin, naringenin(3 → 6″)chrysoeriol, liovil 4-O-β-glucopyranoside, 2,6-dimethoxy cinnamic acid, (E)-4-(3-hydroxy-2,2-dimethylchroman-6-yl)but-3-en-2-one and (E)-4-(4-(((E)-4-hydroxy-3-methylbut-2-en-1-yl)oxy)phenyl)but-3-en-2-one, have been identified from fruits of N. ossifragum for the first time. In addition, the rare natural product 4-hydroxy-3-(3-methylbut-2-enyl)benzaldehyde and the five known compounds 4-hydroxycinnamic acid, quercetin 3,3'-dimethyl ether, quercetin 3,7-dimethyl ether, chrysoeriol 7-O-β-glucopyranoside and the di-C-glycosylflavone isoschaftoside were all characterized for the first time from the fruits of N. ossifragum. The discovery of sufficient amounts of 4-hydroxy-3-(3-methylbut-2-enyl)benzaldehyde in fresh plant material of N. ossifragum to allow complete structure elucidation by NMR and HRMS supports the possibility that fungi associated with N. ossifragum may be able to produce enough toxins to play a significant role in the pathogenicity of N. ossifragum. 4-Hydroxy-3-(3-methylbut-2-enyl)benzaldehyde showed mild toxicity towards normal rat kidney (NRK) and more profound activity towards MOLM13 acute myeloid leukemia cells (IC₅₀ = 430 μM and 68 μM, respectively). Naringenin(3 → 6″)luteolin had IC₅₀ of 230 μM towards NRK cells, and 115 μM towards MOLM13 cells. Microscopic evaluation suggests that these two compounds induce cell death by different mechanisms.

Proceedings of the Frontiers of Retrovirology Conference 2016

Oral presentations

Session 1: Entry & uncoating

O1 Host cell polo-like kinases (PLKs) promote early prototype foamy virus (PFV) replication

Irena Zurnic, Sylvia Hütter, Ute Lehmann, Nicole Stanke, Juliane Reh, Tobias Kern, Fabian Lindel, Gesche Gerresheim, Martin Hamann, Erik Müllers, Paul Lesbats, Peter Cherepanov, Erik Serrao, Alan Engelman, Dirk Lindemann

O2 A novel entry/uncoating assay reveals the presence of at least two species of viral capsids during synchronized HIV-1 infection

Claire Da Silva Santos, Kevin Tartour, Andrea Cimarelli

O3 Dynamics of nuclear envelope association and nuclear import of HIV-1 complexes

Rya Burdick, Jianbo Chen, Jaya Sastri, Wei-Shau Hu, Vinay Pathak

O4 Human papillomavirus protein E4 potently enhances the susceptibility to HIV infection

Oliver T. Keppler

Session 2: Reverse transcription & integration

O5 Structure and function of HIV-1 integrase post translational modifications

Karine Pradeau, Sylvia Eiler, Nicolas Levy, Sarah Lennon, Sarah Cianferani, Stéphane Emiliani, Marc Ruff

O6 Regulation of retroviral integration by RNA polymerase II associated factors and chromatin structure

Vincent Parissi

Session 3: Transcription and latency

O7 A novel single-cell analysis pipeline to identify specific biomarkers of HIV permissiveness

Sylvie Rato, Antonio Rausell, Miguel Munoz, Amalio Telenti, Angela Ciuffi

O8 A capsid-dependent integration program linking T cell activation to HIV-1 gene expression

Alexander Zhyvoloup, Anat Melamed, Ian Anderson, Delphine Planas, Janos Kriston-Vizi, Robin Ketteler, Chen-Hsuin Lee, Andy Merritt, Petronela Ancuta, Charles Bangham, Ariberto Fassati

O9 Characterisation of new RNA polymerase III and RNA polymerase II transcriptional promoters in the Bovine Leukemia Virus genome

Anthony Rodari, Benoit Van Driessche, Mathilde Galais, Nadége Delacourt, Sylvain Fauquenoy, Caroline Vanhulle, Anna Kula, Arsène Burny, Olivier Rohr, Carine Van Lint

O10 Tissue-specific dendritic cells differentially modulate latent HIV-1 reservoirs

Thijs van Montfort, Renee van der Sluis, Dave Speijer, Ben Berkhout

Session 4: RNA trafficking & packaging

O11 A novel cis-acting element affecting HIV replication

Bo Meng, Andrzej Rutkowski, Neil Berry, Lars Dölken, Andrew Lever

O12 Tolerance of HIV’s late gene expression towards stepwise codon adaptation

Thomas Schuster, Benedikt Asbach, Ralf Wagner

Session 5: Assembly & release

O13 Importance of the tax-inducible actin-bundling protein fascin for transmission of human T cell leukemia virus Type 1 (HTLV-1)

Christine Gross, Veit Wiesmann, Martina Kalmer, Thomas Wittenberg, Jan Gettemans, Andrea K. Thoma-Kress

O14 Lentiviral nef proteins antagonize TIM-mediated inhibition of viral release

Minghua Li, Eric O. Freed, Shan-Lu Liu

Session 6: Pathogenesis & evolution

O15 SEVI and semen prolong the half-life of HIV-1

Janis Müller, Jan Münch

O16 CD169⁺ macrophages mediate retrovirus trans-infection of permissive lymphocytes to establish infection in vivo

Xaver Sewald, Pradeep Uchil, Mark Ladinsky, Jagadish Beloor, Ruoxi Pi, Christin Herrmann, Nasim Motamedi, Thomas Murooka, Michael Brehm, Dale Greiner, Thorsten Mempel, Pamela Bjorkman, Priti Kumar, Walther Mothes

O17 Efficient replication of a vpu containing SIVagm construct in African Green Monkeys requires an HIV-1 nef gene

Simone Joas, Erica Parrish, Clement Wesley Gnanadurai, Edina Lump, Christina M. Stürzel, Nicholas F. Parrish, Ulrike Sauermann, Katharina Töpfer, Tina Schultheiss, Steven Bosinger, Guido Silvestri, Cristian Apetrei, Nicholas Huot, Michaela Müller-Trutwin, Daniel Sauter, Beatrice H. Hahn, Christiane Stahl-Hennig, Frank Kirchhoff

O18 Reprogramming initiates mobilization of endogenous mutagenic LINE-1, Alu and SVA retrotransposons in human induced pluripotent stem cells with consequences for host gene expression

Gerald Schumann, Sabine Jung-Klawitter, Nina V. Fuchs, Kyle R. Upton, Martin Muñoz-Lopez, Ruchi Shukla, Jichang Wang, Marta Garcia-Canadas, Cesar Lopez-Ruiz, Daniel J. Gerhardt, Attila Sebe, Ivana Grabundzija, Patricia Gerdes, Sylvia Merkert, Andres Pulgarin, Anja Bock, Ulrike Held, Anett Witthuhn, Alexandra Haase, Ernst J. Wolvetang, Ulrich Martin, Zoltán Ivics, Zsuzsanna Izsvák, J. Garcia-Perez, Geoffrey J. Faulkner

O19 NF-κB activation induces expression of human endogenous retrovirus and particle production

Tara Hurst, Aris Katzourakis, Gkikas Magiorkinis

Session 7a and b: Innate sensing & intrinsic immunity

O20 Identification of the phosphatase acting on T592 in SAMHD1 during M/G₁ transition

Kerstin Schott, Rita Derua, Janna Seifried, Andreas Reuter, Heike Schmitz, Christiane Tondera, Alberto Brandariz-Nuñez, Felipe Diaz-Griffero, Veerle Janssens, Renate König

O21 Vpx overcomes a SAMHD1-independent block to HIV reverse transcription that is specific to resting CD4 T cells

Hanna-Mari Baldauf, Lena Stegmann, Sarah-Marie Schwarz, Maud Trotard, Margarethe Martin, Gina Lenzi, Manja Burggraf, Xiaoyu Pan, Oliver I. Fregoso, Efrem S. Lim, Libin Abraham, Elina Erikson, Laura Nguyen, Ina Ambiel, Frank Rutsch, Renate König, Baek Kim, Michael Emerman, Oliver T. Fackler, Oliver T. Keppler

O22 The role of SAMHD1 in antiviral restriction and immune sensing in the mouse

Sabine Wittmann, Rayk Behrendt, Bianca Volkmann, Kristin Eissmann, Thomas Gramberg

O23 T cells expressing reduced restriction factors are preferentially infected in therapy naïve HIV-1 patients

Sebastian Bolduan, Herwig Koppensteiner, Stefanie Regensburg, Ruth Brack-Werner, Rika Draenert, Michael Schindler

O24 cGAS-mediated innate immunity spreads through HIV-1 env-induced membrane fusion sites from infected to uninfected primary HIV-1 target cells

Aurélie Ducroux, Shuting Xu, Aparna Ponnurangam, Sergej Franz, Angelina Malassa, Ellen Ewald, Christine Goffinet

O25 Perturbation of innate RNA and DNA sensing by human T cell leukemia virus type 1 oncoproteins

Sin-Yee Fung, Ching-Ping Chan, Chun-Kit Yuen, Kin-Hang Kok, Chin-Ping Chan, Dong-Yan Jin

O26 Induction and anti-viral activity of Interferon α subtypes in HIV-1 infection

Ulf Dittmer

O27 Vpu-mediated counteraction of tetherin is a major determinant of HIV-1 interferon resistance

Dorota Kmiec, Shilpa Iyer, Christina Stürzel, Daniel Sauter, Beatrice Hahn, Frank Kirchhoff

O28 DNA repair protein Rad18 restricts HIV-1 and LINE-1 life cycle

Yasuo Ariumi, Mariko Yasuda-Inoue, Koudai Kawano, Satoshi Tateishi, Priscilla Turelli

O29 Natural mutations in IFITM3 allow escape from post-translational regulation and toggle antiviral specificity

Alex Compton, Nicolas Roy, Françoise Porrot, Anne Billet, Nicoletta Casartelli, Jacob Yount, Chen Liang, Oliver Schwartz

Session 8: Adaptive immunity & immune evasion

O30 Observing evolution in HIV-1 infection: phylogenetics and mutant selection windows to infer the influence of the autologous antibody response on the viral quasispecies

Carsten Magnus, Lucia Reh, Penny Moore, Therese Uhr, Jacqueline Weber, Lynn Morris, Alexandra Trkola

O31 Dose and subtype specific analyses of the anti-HIV effects of IFN-alpha family members

Rashel V. Grindberg, Erika Schlaepfer, Gideon Schreiber, Viviana Simon, Roberto F. Speck

Session 9: Novel antiviral strategies

O32 LEDGIN-mediated inhibition of the integrase-LEDGF/p75 interaction reduces reactivation of residual latent HIV

Zeger Debyser, Lenard Vranckx, Jonas Demeulemeester, Suha Saleh, Eric Verdin, Anna Cereseto, Frauke Christ, Rik Gijsbers

O33 NKG2D-mediated clearance of reactivated viral reservoirs by natural killer cells

O34 Inhibition of HIV reactivation in brain cells by AAV-mediated delivery of CRISPR/Cas9

O35 CRISPR-Cas9 as antiviral: potent HIV-1 inhibition, but rapid virus escape and the subsequent design of escape-proof antiviral strategies

Ben Berkhout, Gang Wang, Na Zhao, Atze T. Das

Session 10: Recent advances in HIV vaccine development

O36 Priming with a potent HIV-1 DNA vaccine frames the quality of T cell and antibody responses prior to a poxvirus and protein boost

Benedikt Asbach, Josef Köstler, Beatriz Perdiguero, Mariano Esteban, Bertram L. Jacobs, David C. Montefiori, Celia C. LaBranche, Nicole L. Yates, Georgia D. Tomaras, Guido Ferrari, Kathryn E. Foulds, Mario Roederer, Gary Landucci, Donald N. Forthal, Michael S. Seaman, Natalie Hawkins, Steven G. Self, Sanjay Phogat, James Tartaglia, Susan W. Barnett, Brian Burke, Anthony D. Cristillo, Song Ding, Jonathan L. Heeney, Giuseppe Pantaleo, Ralf Wagner

O37 Passive immunisation with a neutralising antibody against HIV-1 Env prevents infection of the first cells in a mucosal challenge rhesus monkey model

Christiane Stahl-Hennig, Viktoria Stab, Armin Ensser, Ulrike Sauermann, Bettina Tippler, Dennis Burton, Matthias Tenbusch, Klaus Überla

O38 HIV antibody Fc-glycoforms drive B cell affinity maturation

Galit Alter, Giuseppe Lofano, Anne-Sophie Dugast, Viraj Kulkarni, Todd Suscovich

Poster presentations

Topic 1: Entry & uncoating

P1 Dynein light chain is required for murine leukemia virus infection

Tatiana Opazo, Felipe Barraza, Diego Herrera, Andrea Garces, Tomas Schwenke, Diego Tapia, Jorge Cancino, Gloria Arriagada

P2 Peptide paratope mimics of the broadly neutralising HIV-1 antibody b12

Christina Haußner, Dominik Damm, Anette Rohrhofer, Barbara Schmidt, Jutta Eichler

P3 Investigating cellular pathways involved in the transmission of HIV-1 between dendritic cells and T cells using RNAi screening techniques

Rebecca Midgley, James Wheeldon, Vincent Piguet

P4 Co-receptor tropism in HIV-1, HIV-2 monotypic and dual infections

Priyanka Khopkar, Megha Rohamare, Smita Kulkarni

P5 Characterisation of the role of CIB1 and CIB2 as HIV-1 helper factors

Ana Godinho-Santos, Allan Hance, Joao Goncalves, Fabrizio Mammano

P6 Buffering deleterious polymorphisms in the highly constrained C2 region of HIV-1 envelope by the flexible V3 domain

Romain Gasser, Meriem Hamoudi, Martina Pellicciotta, Zhicheng Zhou, Clara Visdeloup, Philippe Colin, Martine Braibant, Bernard Lagane, Matteo Negroni

P7 Entry inhibition of HERV-K(HML-2) by an Env-IgG fusion protein

Jula Wamara, Norbert Bannert

Topic 2: Reverse transcription & integration

P8 The R263K/H51Y resistance substitutions in HIV integrase decreases levels of integrated HIV DNA over time

Thibault Mesplede, Nathan Osman, Kaitlin Anstett, Jiaming Calvin Liang, Hanh Thi Pham, Mark Wainberg

P9 The Retrovirus Integration Database (RID)

Wei Shao, Jigui Shan, Mary Kearney, Xiaolin Wu, Frank Maldarelli, John Mellors, Brian Luke, John Coffin, Stephen Hughes

P10 The small molecule 3G11 inhibits HIV-1 reverse transcription

Thomas Fricke, Silvana Opp, Caitlin Shepard, Dmitri Ivanov, Baek Kim, Jose Valle-Casuso, Felipe Diaz-Griffero

P11 Dual and opposite regulation of HIV-1 integration by hRAD51: impact on therapeutical approaches using homologous DNA repair modulators

Vincent Parissi

P12 A flexible motif essential for integration by HIV-1 integrase

Marine Kanja, Pierre Cappy, Matteo Negroni, Daniela Lener

P13 Interaction between HIV-1 integrase and the host protein Ku70: identification of the binding site and study of the influence on integrase-proteasome interplay

Ekaterina Knyazhanskaya, Andrey Anisenko, Timofey Zatsepin, Marina Gottikh

P14 Normalisation based method for deep sequencing of somatic retroelement integrations in human genome

Alexander Komkov, Anastasia Minervina, Gaiaz Nugmanov, Vadim Nazarov, Konstantin Khodosevich, Ilgar Mamedov, Yuri Lebedev

Topic 3: Transcription and latency

P15 BCA2/RABRING7 restricts HIV-1 transcription by preventing the nuclear translocation of NF-κB

Marta Colomer-Lluch, Ruth Serra-Moreno

P16 MATR3 post-transcriptional regulation of HIV-1 transcription during latency

Ambra Sarracino, Anna Kula, Lavina Gharu, Alexander Pasternak, Carine Van Lint, Alessandro Marcello

P17 HIV-1 tat intersects the SUMO pathway to regulate HIV-1 promoter activity

Ann Marie McCartin, Anurag Kulkarni, Valentin Le Douce, Virginie Gautier

P18 Conservation in HIV-1 Vpr guides tertiary gRNA folding and alternative splicing

Ann Baeyens, Evelien Naessens, Anouk Van Nuffel, Karin Weening, Anne-Marie Reilly, Eva Claeys, Wim Trypsteen, Linos Vandekerckhove, Sven Eyckerman, Kris Gevaert, Bruno Verhasselt

P19 The majority of reactivatable latent HIV are genetically distinct

Hoi Ping Mok, Nicholas Norton, Axel Fun, Jack Hirst, Mark Wills, Andrew Lever

P20 Do mutations in the tat exonic splice enhancer contribute to HIV-1 latency?

Nicholas Norton, Hoi Ping Mok, Jack Hirst, Andrew Lever

P21 Culture-to-Ct: A fast and direct RT-qPCR HIV gene reactivation screening method using primary T cell culture

Valentin Le Douce, Ann Marie McCartin, Virginie Gautier

P22 A novel approach to define populations of early silenced proviruses

Dalibor Miklik, Filip Senigl, Jiri Hejnar

Topic 4: RNA trafficking & packaging

P23 Functional analysis of the structure and conformation of HIV-1 genome RNA DIS

Jun-ichi Sakuragi, Sayuri Sakuragi, Masaru Yokoyama, Tatsuo Shioda, Hironori Sato

P24 Regulation of foamy viral env splicing controls gag and pol expression

Jochen Bodem, Rebecca Moschall, Sarah Denk, Steffen Erkelenz, Christian Schenk, Heiner Schaal

Topic 5: Assembly & release

P25 Transfer of HTLV-1 p8 to target T cells depends on VASP: a novel interaction partner of p8

Norbert Donhauser, Ellen Socher, Sebastian Millen, Heinrich Sticht, Andrea K. Thoma-Kress

P26 COL4A1 and COL4A2 are novel HTLV-1 tax targets with a putative role in virus transmission

Christine Gross, Sebastian Millen, Melanie Mann, Klaus Überla, Andrea K. Thoma-Kress

P27 The C terminus of foamy virus gag protein is required for particle formation, and virus budding: starting assembly at the C terminus?

Guochao Wei, Matthew J. Betts, Yang Liu, Timo Kehl, Robert B. Russell, Martin Löchelt

P28 Generation of an antigen-capture ELISA and analysis of Rec and Staufen-1 effects on HERV-K(HML-2) virus particle production

Oliver Hohn, Saeed Mostafa, Kirsten Hanke, Stephen Norley, Norbert Bannert

P29 Antagonism of BST-2/tetherin is a conserved function of primary HIV-2 Env glycoproteins

Chia-Yen Chen, Masashi Shingai, Pedro Borrego, Nuno Taveira, Klaus Strebel

P30 Mutations in the packaging signal region of the HIV-1 genome cause a late domain mutant phenotype

Chris Hellmund, Bo Meng, Andrew Lever

P31 p6 regulates membrane association of HIV-1 gag

Melanie Friedrich, Friedrich Hahn, Christian Setz, Pia Rauch, Kirsten Fraedrich, Alina Matthaei, Petra Henklein, Maximilian Traxdorf, Torgils Fossen, Ulrich Schubert

Topic 6: Pathogenesis & evolution

P32 Molecular and structural basis of protein evolution during viral adaptation

Aya Khwaja, Meytal Galilee, Akram Alian

P33 HIV-1 enhancement and neutralisation by soluble gp120 and its role for the selection of the R5-tropic “best fit”

Birco Schwalbe, Heiko Hauser, Michael Schreiber

P34 An insertion of seven amino acids in the Env cytoplasmic tail of Human Immunodeficiency Virus type 2 (HIV-2) selected during disease progression enhances viral replication

François Dufrasne, Mara Lucchetti, Patrick Goubau, Jean Ruelle

P35 Cell-associated HIV-1 unspliced to multiply spliced RNA ratio at 12 weeks ART correlates with markers of immune activation and apoptosis and predicts the CD4 T-cell count at 96 weeks ART

Mirte Scherpenisse, Ben Berkhout, Alexander Pasternak

P36 Faster progression in non-B subtype HIV-1-infected patients than Korean subclade of subtype B is accompanied by higher variation and no induction of gross deletion in non-B nef gene by Korean red ginseng treatment

Young-Keol Cho, Jungeun Kim, Daeun Jeong

P37 Aberrant expression of ERVWE1 endogenous retrovirus and overexpression of TET dioxygenases are characteristic features of seminoma

Katerina Trejbalova, Martina Benesova, Dana Kucerova, Zdenka Vernerova, Rachel Amouroux, Petra Hajkova, Jiri Hejnar

P38 Life history of the oldest lentivirus: characterisation of ELVgv integrations and the TRIM5 selection pattern in dermoptera

Daniel Elleder, Tomas Hron, Helena Farkasova, Abinash Padhi, Jan Paces

P39 Characterisation of a highly divergent endogenous retrovirus in the equine germ line

Henan Zhu, Robert Gifford, Pablo Murcia

P40 The emergence of pandemic retroviral infection in small ruminants

Maria Luisa Carrozza, Anna-Maria Niewiadomska, Maurizio Mazzei, Mounir Abi-Said, Joseph Hughes, Stéphane Hué, Robert Gifford

P41 Near full-length genome (NFLG) Characterisation of HIV-1 subtype B identified in South Africa

Adetayo Obasa, Graeme Jacobs, Susan Engelbrecht

P42 Acquisition of Vpu-mediated tetherin antagonism by an HIV-1 group O strain

Katharina Mack, Kathrin Starz, Daniel Sauter, Matthias Geyer, Frederic Bibollet-Ruche, Christina Stürzel, Marie Leoz, Jean Christophe Plantier, Beatrice H. Hahn, Frank Kirchhoff

P43 The human endogenous retrovirus type K is involved in cancer stem cell markers expression and in human melanoma malignancy

Ayele Argaw-Denboba, Emanuela Balestrieri, Annalucia Serafino, Ilaria Bucci, Chiara Cipriani, Corrado Spadafora, Paolo Sinibaldi-Vallebona, Claudia Matteucci

P44 Natural infection of Indian non-human primates by unique lentiviruses

S. Nandi Jayashree, Ujjwal Neogi, Anil K. Chhangani, Shravan Sing Rathore, Bajrang R. J. Mathur

P45 Free cervical cancer screening among HIV-positive women receiving antiretroviral treatment in Nigeria

Adeyemi Abati

P46 Molecular evolutionary status of feline immunodeficiency virus in Turkey

B. Taylan Koç, Tuba Çiğdem Oğuzoğlu

Topic 7: Innate sensing & intrinsic immunity

P47 Cell-to-cell contact with HTLV-1-infected T cells reduces dendritic cell immune functions and contributes to infection in trans.

Takatoshi Shimauchi, Stephan Caucheteux, Jocelyn Turpin, Katja Finsterbusch, Charles Bangham, Yoshiki Tokura, Vincent Piguet

P48 Deciphering the mechanisms of HIV-1 exacerbation induced by Mycobacterium tuberculosis in monocytes/macrophages

Shanti Souriant, Luciana Balboa, Karine Pingris, Denise Kviatcowsky, Brigitte Raynaud-Messina, Céline Cougoule, Ingrid Mercier, Marcelo Kuroda, Pablo González-Montaner, Sandra Inwentarz, Eduardo Jose Moraña, Maria del Carmen Sasiain, Olivier Neyrolles, Isabelle Maridonneau-Parini, Geanncarlo Lugo-Villarino, Christel Vérollet

P49 The SAMHD1-mediated inhibition of LINE-1 retroelements is regulated by phosphorylation

Alexandra Herrmann, Sabine Wittmann, Caitlin Shepard, Dominique Thomas, Nerea Ferreirós Bouzas, Baek Kim, Thomas Gramberg

P50 Activities of nuclear envelope protein SUN2 in HIV infection

Xavier Lahaye, Anvita Bhargava, Takeshi Satoh, Matteo Gentili, Silvia Cerboni, Aymeric Silvin, Cécile Conrad, Hakim Ahmed-Belkacem, Elisa C. Rodriguez, Jean-François Guichou, Nathalie Bosquet, Matthieu Piel, Roger Le Grand, Megan King, Jean-Michel Pawlotsky, Nicolas Manel

P51 Activation of TLR7/8 with a small molecule agonist induces a novel restriction to HIV-1 infection of monocytes

Henning Hofmann, Benedicte Vanwalscappel, Nicolin Bloch, Nathaniel Landau

P52 Steady state between the DNA polymerase and Rnase H domain activities of reverse transcriptases determines the sensitivity of retroviruses to inhibition by APOBEC3 proteins

Stanislav Indik, Benedikt Hagen

P53 HIV restriction in mature dendritic cells is related to p21 induction and p21-mediated control of the dNTP pool and SAMHD1 activity.

José Carlos Valle-Casuso, Awatef Allouch, Annie David, Françoise Barré-Sinoussi, Michaela Müller-Trutwin, Monsef Benkirane, Gianfranco Pancino, Asier Saez-Cirion

P54 IFITM protens restrict HIV-1 protein synthesis

Wing-Yiu Lee, Chen Liang, Richard Sloan

P55 Characterisation and functional analysis of the novel restriction factor Serinc5

Bianca Schulte, Silvana Opp, Felipe Diaz-Griffero

P56 piRNA sequences are common in Human Endogenous Retroviral Sequences (HERVs): An antiretroviral restriction mechanism?

Jonas Blomberg, Luana Vargiu, Patricia Rodriguez-Tomé, Enzo Tramontano, Göran Sperber

P57 Ferroportin restricts HIV-1 infection in sickle cell disease

Namita Kumari, Tatiana Ammosova, Sharmeen Diaz, Patricia Oneal, Sergei Nekhai

P58 APOBEC3G modulates the response to antiretroviral drugs in humanized mice

Audrey Fahrny, Gustavo Gers-Huber, Annette Audigé, Roberto F. Speck, Anitha Jayaprakash, Ravi Sachidanandam, Matt Hernandez, Marsha Dillon-White, Viviana Simon

P59 High-throughput epigenetic analysis of evolutionarily young endogenous retrovirus presents in the mule deer (Odocoileus hemionus) genome

Tomas Hron, Helena Farkasova, Daniel Elleder

P60 Characterisation of the expression of novel endogenous retroviruses and immune interactions in a macaque model

Neil Berry, Emmanuel Maze, Claire Ham, Neil Almond, Greg Towers, Robert Belshaw

P61 HIV-1 restriction by orthologs of SERINC3 and SERINC5

Patrícia de Sousa-Pereira, Joana Abrantes, Massimo Pizzato, Pedro J. Esteves, Oliver T. Fackler, Oliver T. Keppler, Hanna-Mari Baldauf

P62 TRIM19/PML restricts HIV infection in a cell type-dependent manner

Bianca Volkmann, Tanja Kahle, Kristin Eissmann, Alexandra Herrmann, Sven Schmitt, Sabine Wittmann, Laura Merkel, Nina Reuter, Thomas Stamminger, Thomas Gramberg

P63 Recent invasion of the mule deer genome by a retrovirus

Helena Farkasova, Tomas Hron, Daniel Elleder

P64 Does the antiviral protein SAMHD1 influence mitochondrial function?

Ilaria Dalla Rosa, Kate Bishop, Antonella Spinazzola, Harriet Groom

P65 cGAMP transfers intercellularly via HIV-1 Env-mediated cell–cell fusion sites and triggers an innate immune response in primary target cells

Shuting Xu, Aurélie Ducroux, Aparna Ponnurangam, Sergej Franz, Gabrielle Vieyres, Mathias Müsken, Thomas Zillinger, Angelina Malassa, Ellen Ewald, Veit Hornung, Winfried Barchet, Susanne Häussler, Thomas Pietschmann, Christine Goffinet

P66 Pre-infection transcript levels of FAM26F in PBMCS inform about overall plasma viral load in acute and postacute phase after SIV-infection

Ulrike Sauermann, Aneela Javed, Nicole Leuchte, Gabriela Salinas, Lennart Opitz, Christiane Stahl-Hennig, Sieghart Sopper

P67 Sequence-function analysis of three T cell receptors targeting the HIV-1 p17 epitope SLYNTVATL

Christiane Mummert, Christian Hofmann, Angela G. Hückelhoven, Silke Bergmann, Sandra M. Müller-Schmucker, Ellen G. Harrer, Jan Dörrie, Niels Schaft, Thomas Harrer

P68 An immunodominant region of the envelope glycoprotein of small ruminant lentiviruses may function as decoy antigen

Laure Cardinaux, M.-L. Zahno, H.-R. Vogt, R. Zanoni, G. Bertoni

P69 Impact of immune activation, immune exhaustion, broadly neutralising antibodies and viral reservoirs on disease progression in HIV-infected children

Maximilian Muenchhoff, Philip Goulder, Oliver Keppler

Topic 9: Novel antiviral strategies

P70 Identification of natural compounds as new antiviral products by bioassay-guided fractionation

Alexandra Herrmann, Stephanie Rebensburg, Markus Helfer, Michael Schindler, Ruth Brack-Werner

P71 The PPARG antagonism disconnects the HIV replication and effector functions in Th17 cells

Yuwei Zhang, Huicheng Chen, Delphine Planas, Annie Bernier, Annie Gosselin, Jean-Pierre Routy, Petronela Ancuta

P72 Characterisation of a multiresistant subtype AG reverse transcriptase: AZT resistance, sensitivity to RNase H inhibitors and inhibitor binding

Birgitta Wöhrl, Anna Schneider, Angela Corona, Imke Spöring, Mareike Jordan, Bernd Buchholz, Elias Maccioni, Roberto Di Santo, Jochen Bodem, Enzo Tramontano, Kristian Schweimer

P73 Insigths into the acetylation pattern of HDAC inhibitors and their potential role in HIV therapy

Christian Schölz, Brian Weinert, Sebastian Wagner, Petra Beli, Yasuyuki Miyake, Jun Qi, Lars Jensen, Werner Streicher, Anna McCarthy, Nicholas Westwood, Sonia Lain, Jürgen Cox, Patrick Matthias, Matthias Mann, James Bradner, Chunaram Choudhary

P74 HPV-derived and seminal amyloid peptides enhance HIV-1 infection and impair the efficacy of broadly neutralising antibodies and antiretroviral drugs

Marcel Stern, Oliver T. Keppler

P75 D(−)lentiginosine inhibits both proliferation and virus expression in cells infected by HTLV-1 in vitro

Elena Valletta, Caterina Frezza, Claudia Matteucci, Francesca Marino-Merlo, Sandro Grelli, Anna Lucia Serafino, Antonio Mastino, Beatrice Macchi

P76 HIV-1 resistance analyses of the Cape Winelands districts, South Africa

Sello Mikasi, Graeme Jacobs, Susan Engelbrecht

Topic 10: Recent advances in HIV vaccine development

P77 Induction of complex retrovirus antigen-specific immune responses by adenovirus-based vectors depends on the order of vector administration

Meike Kaulfuß, Sonja Windmann, Wibke Bayer

P78 Direct impact of structural properties of HIV-1 Env on the regulation of the humoral immune response

Rebecca Heß, Michael Storcksdieck gen. Bonsmann, Viktoria Stab, Carsten Kirschning, Bernd Lepenies, Matthias Tenbusch, Klaus Überla

P79 Lentiviral virus-like particles mediate gerenration of T-follicular helper cells in vitro

Anne Kolenbrander, Klaus Überla, Vladimir Temchura

P80 Recruitment of HIV-1 Vpr to DNA damage sites and protection of proviral DNA from nuclease activity

Kenta Iijima, Junya Kobayashi, Yukihito Ishizaka

New Polyfunctional Phragmalin Limonoids from Neobeguea mahafalensis

Neobeguea mahafalensis is used as a medicinal plant in Madagascar. A decoction of the stem bark of this species is reported to treat back pain. Recently, it was reported that a decoction of the root bark, containing two novel phragmalin limonoids as identified active constituents, exhibited an extraordinarily high potency and remarkably long duration in augmenting sexual activity in male rodents.From the dichloromethane extract of the root barks of N. mahafalensis, nine phragmalin limonoids were isolated, of which eight were novel compounds. The structures were established mainly by extensive use of 2D NMR spectroscopic techniques and high-resolution mass spectrometry. One of the new compounds named dodoguin displayed sleep-inducing activity in Swiss albino mice. The amount of 3-10 mg/kg of this compound induced sleep 18-22 min after its administration with a duration of 16-18 min.

First identification of natural products from the African medicinal plant Zamioculcas zamiifolia - A drought resistant survivor through millions of years

Zamioculcas zamiifolia, an unusually drought resistant medicinal plant native to tropical east Africa and subtropical southeast Africa, including the countries Kenya, Malawi, Mozambique, South-Africa, Tanzania and Zimbabwe, is described as a living fossil which may have evolved as early as 42 million years ago. It belongs to the notoriously toxic family Araceae giving it, through association, a reputation for being toxic; despite little or no systematic evidence exists to support this claim. As an ancient plant it has sustained substantial climate changes and attacks from millions of generations of pathogenic microorganisms, which encouraged search for novel natural products from this source. Seven natural products have been characterized from leaves and petioles of Z. zamiifolia, including the novel main compound of the leaves, apigenin 6-C-(6″-(3-hydroxy-3-methyl-glutaroyl)-ß-glucopyranoside). The structure determinations were based on extensive use of 2D NMR spectroscopic techniques and high-resolution mass spectrometry. Initial toxicological experiment on extracts from Z. zamiifolia using brine shrimp lethality assay did not indicate lethality to the shrimps providing disproving evidence for the assumption of Z. zamiifolia's toxic character.

Pseudoaeruginosins, nonribosomal peptides in Nodularia spumigena

Nodularia spumigena is a filamentous cyanobacterium that forms toxic blooms in brackish waters around the world through the production of the pentapeptide toxin nodularin. This cyanobacterium also produces large amounts of protease inhibitors belonging to the aeruginosin and spumigin families. Here we report the discovery of previously unknown protease inhibitors, pseudoaeruginosins NS1 (1) and NS2 (2), from 33 strains of N. spumigena isolated from the Baltic Sea. Pseudoaeruginosin NS1 (1) and NS2 (2) contain hexanoic acid, tyrosine, 4-methylproline, and argininal/argininol. The chemical structure of the two pseudoaeruginosins was verified by thorough comparison of the liquid chromatography-mass spectrometry (LC-MS) analyses of the extracts from the N. spumigena strains with synthetic peptides. The structures of the synthetic pseudoaeruginosins were confirmed using nuclear magnetic resonance spectroscopy. Surprisingly, the structure of pseudoaeruginosin NS1 (1) and NS2 (2) combines features of both aeruginosins and spumigins, suggesting that they have been produced through the joint action of both the spumigin and aeruginosin biosynthesis pathways. We screened with polymerase chain reaction and LC-MS 68 N. spumigena strains from the Baltic Sea and Australia. Pseudoaeruginosins were present in half of the Baltic Sea strains but were not found from the Australian strains. The production of pseudoaeruginosin seems to be coupled to the production of aeruginosins and 4-methylproline-containing spumigins. Pseudoaeruginosin NS1 was found to be as potent trypsin inhibitor as the most potent aeruginosins and spumigins with an IC50 of 0.19 ± 0.04 μM. This finding suggests that cooperation between the spumigin and aeruginosin biosynthetic pathways results in hybrid pseudoaeruginosin peptides.

The native structure of annexin A2 peptides in hydrophilic environment determines their anti-angiogenic effects

The progression of aggressive cancer occurs via angiogenesis and metastasis makes these processes important targets for the development of anti-cancer agents. However, recent studies have raised the concern that selective inhibition of angiogenesis results in a switch towards increased tumour growth and metastasis. Since Annexin A2 (AnxA2) is involved in both angiogenesis and metastasis, it may serve as an ideal target for the simultaneous inhibition of both processes. Based on the discovery that domains I (D(I)) and IV (D(IV)) of AnxA2 are potent inhibitors of angiogenesis, we designed seven peptides derived from these domains based on AnxA2 crystal structures. The peptides were expressed as fusion peptides to increase their folding and solubility. Light scattering, far-UV circular dichroism and thermal transition analyses were employed to investigate their aggregation tendencies, α-helical propensity and stability, respectively. 2,2,2-trifluoroethanol (50%) increased the α-helical propensities of all peptides, indicating that they may favour a hydrophobic environment, but did not enhance their thermal stability. D(I)-P2 appears to be the most stable and folded peptide in a hydrophilic environment. The secondary structure of D(I)-P2 was confirmed by nuclear magnetic resonance spectra. The effect of the seven AnxA2 peptides on the formation and integrity of capillary-like networks was studied in a co-culture system mimicking many of the angiogenesis-related processes. Notably, D(I)-P2 inhibited significantly network formation in this system, indicating that the folded D(I)-P2 peptide interferes with vascular endothelial growth factor-dependent pro-angiogenic processes. Thus, this peptide has the potential of being developed further as an anti-angiogenic drug.

Growing with dinosaurs: natural products from the Cretaceous relict Metasequoia glyptostroboides Hu & Cheng-a molecular reservoir from the ancient world with potential in modern medicine

After the sensational rediscovery of living exemplars of the Cretaceous relict Metasequoia glyptostroboides-a tree previously known exclusively from fossils from various locations in the northern hemisphere, there has been an increasing interest in discovery of novel natural products from this unique plant source. This article includes the first complete compilation of natural products reported from M. glyptostroboides during the entire period in which the tree has been investigated (1954-2014) with main focus on the compounds specific to this plant source. Studies on the biological activity of pure compounds and extracts derived from M. glyptostroboides are reviewed for the first time. The unique potential of M. glyptostroboides as a source of bioactive constituents is founded on the fact that the tree seems to have survived unchanged since the Cretaceous era. Since then, its molecular defense system has resisted the attacks of millions of generations of pathogens. In line with this, some recent landmarks in Metasequoia paleobotany are covered. Initial spectral analysis of recently discovered intact 53 million year old wood and amber of Metasequoia strongly indicate that the tree has remained unchanged for millions of years at the molecular level.

Reversible ketomethylene-based inhibitors of human neutrophil proteinase 3

Neutrophil serine proteases, proteinase 3 (PR3) and human neutrophil elastase (HNE), are considered as targets for chronic inflammatory diseases. Despite sharing high sequence similarity, the two enzymes have different substrate specificities and functions. While a plethora of HNE inhibitors exist, PR3 specific inhibitors are still in their infancy. We have designed ketomethylene-based inhibitors for PR3 that show low micromolar IC50 values. Their synthesis was made possible by amending a previously reported synthesis of ketomethylene dipeptide isosteres to allow for the preparation of derivatives suitable for solid phase peptide synthesis. The best inhibitor (Abz-VADnV[Ψ](COCH2)ADYQ-EDDnp) was found to be selective for PR3 over HNE and to display a competitive and reversible inhibition mechanism. Molecular dynamics simulations show that the interactions between enzyme and ketomethylene-containing inhibitors are similar to those with the corresponding substrates. We also confirm that N- and C-terminal FRET groups are important for securing high inhibitory potency toward PR3.

Balticidins A-D, antifungal hassallidin-like lipopeptides from the Baltic Sea cyanobacterium Anabaena cylindrica Bio33

Balticidins A-D (1-4), four new antifungal lipopeptides, were isolated from the laboratory-cultivated cyanobacterium Anabaena cylindrica strain Bio33 isolated from a water sample collected from the Baltic Sea, Rügen Island, Germany. Fractionation of the 50% aqueous MeOH extract was performed by bioassay-guided silica gel column chromatography followed by SPE and repeated reversed-phase HPLC. The main fraction containing the compounds exhibited a strong and specific antifungal activity with inhibition zones in an agar-diffusion assay from 21 to 32 mm against Candida albicans, Candida krusei, Candida maltosa, Aspergillus fumigatus, Microsporum gypseum, Mucor sp., and Microsporum canis. The structures were elucidated by multidimensional (1)H and (13)C NMR spectroscopy, HRESIMS, amino acid analysis, and sugar analysis. Spectroscopic data analysis afforded an unambiguous sequence of R.CHO(S1).CHOH.CONH-Thr(1)-Thr(2)-Thr(3)-HOTyr(4)-Dhb(5)-D-Gln(6)-Gly(7)-NMeThr(8)(S2)-L-Gln COOH(9), in which Dhb is dehydroaminobutyric acid, S1 is d(-)-arabinose-(3-1)-D-(+)-galacturonic acid, S2 is D-(+)-mannose, and R is the aliphatic residue -C13H26Cl or -C13H27. Besides NMeThr, D-allo-Thr, D-Thr, and L-Thr were identified, but the position of the enantiomers in the sequence is not clear. The four balticidins differ in their cyclic (2, 4)/linear (1, 3) core and the presence (1, 2)/absence (3, 4) of chlorine in the aliphatic unit.

Novel GHB-derived natural products from European mistletoe (Viscum album)

CONTEXT

The European white-berry mistletoe [Viscum album L. (Loranthaceae)] is among the oldest known medicinal plants. At present the most important application of mistletoe extracts is in the treatment of cancer. However, natural products specific to mistletoe have rarely been encountered in the current literature.

OBJECTIVE

To discover novel natural products specific to European mistletoe.

MATERIALS AND METHODS

European mistletoe was extracted with methanol, purified to partition against diethyl ether and further purified with XAD-7 column chromatography. Pure compounds were separated by Sephadex column chromatography and preparative HPLC. The structures of the novel compounds were established using a combination of several 2D NMR spectroscopic techniques and mass spectrometry.

RESULTS

A new type of natural product derived from the methyl ester of γ-hydroxybutyric acid (GHB) coupled to hydroxybenzoic acids, namely 3-(3'-carbomethoxypropyl) gallic acid and 3-(3'-carbomethoxypropyl)-7→3″-protocatechoyl galloate were characterized from European white-berry mistletoe. Condensation of the 3-hydroxyl of gallic acid with the 4-hydroxyl of GHB significantly reduced the radical scavenging properties of the former compound.

DISCUSSION AND CONCLUSION

The characterized compounds define a novel group of natural products that may be of particular interest because it appears that the two new compounds are not closely related to any known natural product.

Influenza A virus protein PB1-F2 from different strains shows distinct structural signatures

The proapoptotic influenza A virus PB1-F2 protein contributes to viral pathogenicity and is present in most human and avian influenza isolates. The structures of full-length PB1-F2 of the influenza strains Pandemic flu 2009 H1N1, 1918 Spanish flu H1N1, Bird flu H5N1 and H1N1 PR8, have been characterized by NMR and CD spectroscopy. The study was conducted using chemically synthesized full-length PB1-F2 protein and fragments thereof. The amino acid residues 30-70 of PR8 PB1-F2 were found to be responsible for amyloid formation of the protein, which could be assigned to formation of β-sheet structures, although α-helices were the only structural features detected under conditions that mimic a membranous environment. At membranous conditions, in which the proteins are found in their most structured state, significant differences become apparent between the PB1-F2 variants investigated. In contrast to Pandemic flu 2009 H1N1 and PR8 PB1-F2, which exhibit a continuous extensive C-terminal α-helix, both Spanish flu H1N1 and Bird flu H5N1 PB1-F2 contain a loop region with residues 66-71 that divides the C-terminus into two shorter helices. The observed structural differences are located to the C-terminal ends of the proteins to which most of the known functions of these proteins have been assigned. A C-terminal helix-loop-helix motif might be a structural signature for PB1-F2 of the highly pathogenic influenza viruses as observed for 1918 Spanish flu H1N1 and Bird flu H5N1 PB1-F2. This signature could indicate the pathological nature of viruses emerging in the future and thus aid in the recognition of these viruses.

HIV-1 p6 - a structured to flexible multifunctional membrane-interacting protein

The human immunodeficiency virus type 1 (HIV-1) p6 protein has recently been recognized as a docking site for several cellular and viral binding partners and is important for the formation of infectious viruses. Most of its known functions are suggested to occur under hydrophobic conditions near the cytoplasmic membrane, where the protein is presumed to exist in its most structured state. Although p6 is involved in manifold specific interactions, the protein has previously been considered to possess a random structure in aqueous solution. We show that p6 exhibits a defined structure with N- and C-terminal helical domains, connected by a flexible hinge region in 100mM dodecylphosphocholine micelle solution at pH 7 devoid of any organic co-solvents, indicating that this is a genuine limiting structural feature of the molecule in a hydrophobic environment. Furthermore, we show that p6 directly interacts with a cytoplasmic model membrane through both N-terminal and C-terminal regions by use of surface plasmon resonance (SPR) spectroscopy. Phosphorylation of Ser-40 located in the center of the C-terminal α-helix does not alter the secondary structure of the protein but amplifies the interaction with membranes significantly, indicating that p6 binds to the polar head groups at the surface of the cytoplasmic membrane. The increased hydrophobic membrane interaction of p6(23-52) S40F correlated with the observed increased amount of the polyprotein Gag in the RIPA insoluble fraction when Ser40 of p6 was mutated with Phe indicating that p6 modulates the membrane interactions of HIV-1 Gag.

Nuclear import of isoforms of the cytomegalovirus kinase pUL97 is mediated by differential activity of NLS1 and NLS2 both acting through classical importin-α binding

The multifunctional protein kinase pUL97 of human cytomegalovirus (HCMV) strongly determines the efficiency of virus replication. Previously, the existence of two pUL97 isoforms that arise from alternative translational initiation and show a predominant nuclear localization was described. Two bipartite nuclear localization sequences, NLS1 and NLS2, were identified in the N terminus of the large isoform, whilst the small isoform exclusively contained NLS2. The current study found the following: (i) pUL97 nuclear localization in HCMV-infected primary fibroblasts showed accumulations in virus replication centres and other nuclear sections; (ii) in a quantitative evaluation system for NLS activity, the large isoform showed higher efficiency of nuclear translocation than the small isoform; (iii) NLS1 was mapped to aa 6-35 and NLS2 to aa 190-213; (iv) using surface plasmon resonance spectroscopy, the binding of both NLS1 and NLS2 to human importin-α was demonstrated, stressing the importance of individual arginine residues in the bipartite consensus motifs; (v) nuclear magnetic resonance spectroscopy of pUL97 peptides confirmed an earlier statement about the functional requirement of NLS1 embedding into an intact α-helical structure; and (vi) a bioinformatics investigation of the solvent-accessible surface suggested a high accessibility of NLS1 and an isoform-specific, variable accessibility of NLS2 for interaction with importin-α. Thus, the nucleocytoplasmic transport mechanism of the isoforms appeared to be differentially regulated, and this may have consequences for isoform-dependent functions of pUL97 during virus replication.

A new protolimonoid from Capuronianthus mahafalensis

From stem barks of Capuronianthus mahafalensis (Meliaceae) endemic to Madagascar, a new protolimonoid named capulin containing a four membered ring in its side chain was isolated by repeated silica gel column chromatography. Its structure was determined by 1D and 2D NMR spectroscopy and high-resolution MS. To the best of our knowledge, this is the first time that a four-membered ring occurs in the side chain of protolimonoids.

HIV-1 p6-Another viral interaction partner to the host cellular protein cyclophilin A

The 52-amino acid human immunodeficiency virus type 1 (HIV-1) p6 protein has previously been recognized as a docking site for several cellular and viral binding factors and is important for the formation of infectious viruses. A particular structural feature of p6 is the notably high relative content of proline residues, located at positions 5, 7, 10, 11, 24, 30, 37 and 49 in the sequence. Proline cis/trans isomerism was detected for all these proline residues to such an extent that more than 40% of all p6 molecules contain at least one proline in a cis conformation. 2D (1)H nuclear magnetic resonance analysis of full-length HIV-1 p6 and p6 peptides established that cyclophilin A (CypA) interacts as a peptidyl-prolyl cis/trans isomerase with all proline residues of p6. Only catalytic amounts of CypA were necessary for the interaction with p6 to occur, strongly suggesting that the observed interaction is highly relevant in vivo. In addition, surface plasmon resonance studies revealed binding of full-length p6 to CypA, and that this binding was significantly stronger than any of its N- or C-terminal peptides. This study demonstrates the first identification of an interaction between HIV-1 p6 and the host cellular protein CypA. The mode of interaction involves both transient enzyme-substrate interactions and a more stable binding. The binding motifs of p6 to Tsg-101, ALIX and Vpr coincide with binding regions and catalytic sites of p6 to CypA, suggesting a potential role of CypA in modulating functional interactions of HIV-1.

The host-pathogen interaction of human cyclophilin A and HIV-1 Vpr requires specific N-terminal and novel C-terminal domains

BACKGROUND

Cyclophilin A (CypA) represents a potential key molecule in future antiretroviral therapy since inhibition of CypA suppresses human immunodeficiency virus type 1 (HIV-1) replication. CypA interacts with the virus proteins Capsid (CA) and Vpr, however, the mechanism through which CypA influences HIV-1 infectivity still remains unclear.

RESULTS

Here the interaction of full-length HIV-1 Vpr with the host cellular factor CypA has been characterized and quantified by surface plasmon resonance spectroscopy. A C-terminal region of Vpr, comprising the 16 residues 75GCRHSRIGVTRQRRAR90, with high binding affinity for CypA has been identified. This region of Vpr does not contain any proline residues but binds much more strongly to CypA than the previously characterized N-terminal binding domain of Vpr, and is thus the first protein binding domain to CypA described involving no proline residues. The fact that the mutant peptide Vpr75-90 R80A binds more weakly to CypA than the wild-type peptide confirms that Arg-80 is a key residue in the C-terminal binding domain. The N- and C-terminal binding regions of full-length Vpr bind cooperatively to CypA and have allowed a model of the complex to be created. The dissociation constant of full-length Vpr to CypA was determined to be approximately 320 nM, indicating that the binding may be stronger than that of the well characterized interaction of HIV-1 CA with CypA.

CONCLUSIONS

For the first time the interaction of full-length Vpr and CypA has been characterized and quantified. A non-proline-containing 16-residue region of C-terminal Vpr which binds specifically to CypA with similar high affinity as full-length Vpr has been identified. The fact that this is the first non-proline containing binding motif of any protein found to bind to CypA, changes the view on how CypA is able to interact with other proteins. It is interesting to note that several previously reported key functions of HIV-1 Vpr are associated with the identified N- and C-terminal binding domains of the protein to CypA.

Highly conserved serine residue 40 in HIV-1 p6 regulates capsid processing and virus core assembly

Background

The HIV-1 p6 Gag protein regulates the final abscission step of nascent virions from the cell membrane by the action of two late assembly (L-) domains. Although p6 is located within one of the most polymorphic regions of the HIV-1 gag gene, the 52 amino acid peptide binds at least to two cellular budding factors (Tsg101 and ALIX), is a substrate for phosphorylation, ubiquitination, and sumoylation, and mediates the incorporation of the HIV-1 accessory protein Vpr into viral particles. As expected, known functional domains mostly overlap with several conserved residues in p6. In this study, we investigated the importance of the highly conserved serine residue at position 40, which until now has not been assigned to any known function of p6.

Results

Consistently with previous data, we found that mutation of Ser-40 has no effect on ALIX mediated rescue of HIV-1 L-domain mutants. However, the only feasible S40F mutation that preserves the overlapping pol open reading frame (ORF) reduces virus replication in T-cell lines and in human lymphocyte tissue cultivated ex vivo. Most intriguingly, L-domain mediated virus release is not dependent on the integrity of Ser-40. However, the S40F mutation significantly reduces the specific infectivity of released virions. Further, it was observed that mutation of Ser-40 selectively interferes with the cleavage between capsid (CA) and the spacer peptide SP1 in Gag, without affecting cleavage of other Gag products. This deficiency in processing of CA, in consequence, led to an irregular morphology of the virus core and the formation of an electron dense extra core structure. Moreover, the defects induced by the S40F mutation in p6 can be rescued by the A1V mutation in SP1 that generally enhances processing of the CA-SP1 cleavage site.

Conclusions

Overall, these data support a so far unrecognized function of p6 mediated by Ser-40 that occurs independently of the L-domain function, but selectively affects CA maturation and virus core formation, and consequently the infectivity of released virions.

The intriguing cyclophilin A-HIV-1 Vpr interaction: prolyl cis/trans isomerisation catalysis and specific binding

Background

Cyclophilin A (CypA) represents a potential target for antiretroviral therapy since inhibition of CypA suppresses human immunodeficiency virus type 1 (HIV-1) replication, although the mechanism through which CypA modulates HIV-1 infectivity still remains unclear. The interaction of HIV-1 viral protein R (Vpr) with the human peptidyl prolyl isomerase CypA is known to occur in vitro and in vivo. However, the nature of the interaction of CypA with Pro-35 of N-terminal Vpr has remained undefined.

Results

Characterization of the interactions of human CypA with N-terminal peptides of HIV-1 Vpr has been achieved using a combination of nuclear magnetic resonace (NMR) exchange spectroscopy and surface plasmon resonance spectroscopy (SPR). NMR data at atomic resolution indicate prolyl cis/trans isomerisation of the highly conserved proline residues Pro-5, -10, -14 and -35 of Vpr are catalyzed by human CypA and require only very low concentrations of the isomerase relative to that of the peptide substrates. Of the N-terminal peptides of Vpr only those containing Pro-35 bind to CypA in a biosensor assay. SPR studies of specific N-terminal peptides with decreasing numbers of residues revealed that a seven-residue motif centred at Pro-35 consisting of RHFPRIW, which under membrane-like solution conditions comprises the loop region connecting helix 1 and 2 of Vpr and the two terminal residues of helix 1, is sufficient to maintain strong specific binding.

Conclusions

Only N-terminal peptides of Vpr containing Pro-35, which appears to be vital for manifold functions of Vpr, bind to CypA in a biosensor assay. This indicates that Pro-35 is essential for a specific CypA-Vpr binding interaction, in contrast to the general prolyl cis/trans isomerisation observed for all proline residues of Vpr, which only involve transient enzyme-substrate interactions. Previously suggested models depicting CypA as a chaperone that plays a role in HIV-1 virulence are now supported by our data. In detail the SPR data of this interaction were compatible with a two-state binding interaction model that involves a conformational change during binding. This is in accord with the structural changes observed by NMR suggesting CypA catalyzes the prolyl cis/trans interconversion during binding to the RHFP³⁵RIW motif of N-terminal Vpr.

Flavone C-glycosides from seeds of fenugreek, Trigonella foenum-graecum L

Fenugreek (Trigonella foenum-graecum L.) is particularly used in Asia, Africa, and Mediterranean countries for its nutritional and medicinal value. The flavone C-glycosides, apigenin 6-C-beta-chinovopyranosyl-8-C-beta-galactopyranoside (6) and apigenin 6-C-beta-xylopyranosyl-8-C-(6'''-O-(3-hydroxy-3-methylglutaroyl)-beta-glucopyranoside) (7), in addition to the known flavone C-glycosides, apigenin 6,8-C-di-beta-galactopyranoside (1), apigenin 6-C-beta-xylopyranosyl-8-C-beta-galactopyranoside (2), apigenin 6-C-beta-arabinopyranosyl-8-C-beta-galactopyranoside (3), luteolin 8-C-beta-glucopyranoside (4), luteolin 6-C-beta-glucopyranoside (5), apigenin 8-C-beta-glucopyranoside (8), apigenin 6-C-beta-glucopyranoside (9), luteolin 8-C-(2''-O-(E)-p-coumaroyl-beta-glucopyranoside) (10), and apigenin 8-C-(2''-O-(E)-p-coumaroyl-beta-glucopyranoside) (11) were isolated from fenugreek seeds. Compounds 1, 5, and 10 were reported for the first time in this species. Signal duplication in the NMR spectra, with exception of spectra of the mono-6-C-substituted compounds, revealed the presence of rotameric conformers, created by rotational hindrance at the C (sp(3))-C (sp(2)) glycosyl-flavone linkage in these flavone C-glycosides.

Structural properties of anthocyanins: rearrangement of C-glycosyl-3-deoxyanthocyanidins in acidic aqueous solutions

Seven C-glycosyl-3-deoxyanthocyanidins were made from their corresponding C-glycosylflavones. The structures of their rearrangement products, which were formed in acidic aqueous solutions, were elucidated. Rotameric conformers were detected for all of the 8-C-glycosyldeoxyanthocyanidins but were absent for their isomeric 6-C-analogues in acidified methanolic NMR solvent. A correlation method based on HPLC-DAD and NMR integration of similar samples made it possible for the first time to determine accurately the proportions of two isomeric 6-C- and 8-C-glycosylflavonoids occurring in mixtures. Each of the C-glycosyldeoxyanthocyanidins established fixed equilibrium proportions with their corresponding A-ring isomer in aqueous solutions, even under relatively strong acidic conditions (pH approximately 1), whether one started with pure 6-C- or 8-C-glycosyl-3-deoxyanthocyanidin. The nature of the aglycone, C-glycosyl moiety, and temperature were found to affect the equilibrium proportions. Increased water content (to a certain level) and temperatures were shown to increase the isomerization rates. The flavylium cations were the only equilibrium forms present at detectable quantities. The significance of rotation of the A-ring during isomerization was confirmed by lack of rearrangement of both 6-C- and 8-C-glycosyl-3-deoxy-5-carboxypyranoanthocyanidins. The intermediary C-ring open forms of the C-glycosyldeoxyanthocyanidins experience fast ring closure to their cyclic forms, which may reduce irreversible degradation reported for open chalcone forms of the common anthocyanins. The stable C-glycosyl-3-deoxyanthocyanidins may thus attract interest as possible colorants in the food industry, etc.

C-glycosylanthocyanidins synthesized from C-glycosylflavones

Nine C-glycosyldeoxyanthocyanidins, 6-C-beta-glucopyranosyl-7-O-methylapigeninidin, 6-C-beta-glucopyranosyl-7-O-methylluteolinidin, 6-C-beta-(2''-O-beta-glucopyranosylglucopyranosyl)-7-O-methylapigeninidin, 6-C-beta-(2''-O-beta-glucopyranosylglucopyranosyl)-7,4'-di-O-methylapigeninidin, 8-C-beta-glucopyranosylapigeninidin, 8-C-beta-(2''-O-alpha-rhamnopyranosylglucopyranosyl)apigeninidin, 8-C-beta-(2''-O-alpha-(4'''-O-acetylrhamnopyranosyl)glucopyranosyl)apigeninidin, 6,8-di-C-beta-glucopyranosylapigeninidin (8), 6,8-di-C-beta-glucopyranosyl-4'-O-methylluteolinidin (9), have been synthesized from their respective C-glycosylflavones (yields between 14% and 32%) by the Clemmensen reduction reaction using zinc-amalgam. The various precursors (C-glycosylflavones) of the C-glycosylanthocyanidins were isolated from either flowers of Iris sibirica L., leaves of Hawthorn 'Crataegi Folium Cum Flore', or lemons and oranges. This is the first time C-glycosylanthocyanidins have been synthesized. The structures of all flavonoids including the flavone rotamers were elucidated by 2D NMR techniques and high-resolution electrospray MS. The distribution of the various structural forms of 8 and 9 are different at pH 1.1, 4.5, and 7.0, however, the two pigments undergoes similar structural transformations at the various pH values. Pigments 8 and 9 with C-C linkages between the sugar moieties and the aglycone, were found to be far more stable towards acid hydrolysis than pelargonidin 3-O-glucoside, which has the typical anthocyanidin C-O linkage between the sugar and aglycone. This stability may extend the present use of anthocyanins as nutraceuticals, pharmaceuticals or colorants.

Synthesis of full length PB1-F2 influenza A virus proteins from 'Spanish flu' and 'bird flu'

The proapoptotic influenza A virus PB1-F2 protein contributes to viral pathogenicity and is present in most human and avian isolates. Previous synthetic protocols have been improved to provide a synthetic full length H1N1 type PB1-F2 protein that is encoded by the 'Spanish flu' isolate and an equivalent protein from an avian host that is representative of a highly pathogenic H5N1 'bird flu' isolate, termed SF2 and BF2, respectively. Full length SF2, different mutants of BF2 and a number of fragments of these peptides have been synthesized by either the standard solid-phase peptide synthesis method or by native chemical ligation of unprotected N- and C-terminal peptide fragments. For SF2 chemical ligation made use of the histidine and the cysteine residues located in positions 41 and 42 of the native sequence, respectively, to afford a highly efficient synthesis of SF2 compared to the standard SPPS elongation method. By-product formation at the aspartic acid residue in position 23 was prevented by specific modifications of the SPPS protocol. As the native sequence of BF2 does not contain a cysteine residue two different mutants of BF2 (Y42C) and BF2 (S47C) with appropriate cysteine exchanges were produced. In addition to the full length molecules, fragments of the native sequences were synthesized for comparison of their physical characteristics with those from the H1N1 human isolate A/Puerto Rico/8/34 (H1N1). All peptides were analyzed by mass spectrometry, (1)H NMR spectroscopy, and SDS-PAGE. The protocols allow the synthesis of significant amounts of PB1-F2 and its related peptides.

The flavonoids of tomatoes

Tomatoes ( Lycopersicon esculentum Mill.) have been recognized as an important source of dietary flavonoids because of a high consumption worldwide. The qualitative and quantitative flavonoid compositions of assorted tomato cultivars including individual quantitative contributions of the five most significant flavonoids have been determined in this work. The dihydrochalcone phloretin 3',5'-di-C-beta-glucopyranoside and the flavonol quercetin 3-O-(2''-O-beta-apiofuranosyl-6''-O-alpha-rhamnopyranosyl-beta-glucopyranoside) were identified for the first time in Solanaceae spp. and found to be among the main flavonoids in all cultivars. Phloretin 3',5'-di-C-glc is the first C-glycoside identified in tomatoes and also the first dihydrochalcone from this species. In addition, chalconaringenin, kaempferol 3-rutinoside, and quercetin 3-rutinoside (rutin), though previously reported to occur in tomato, were fully characterized by extensive use of 2D NMR techniques and high-resolution LCMS. The total flavonoid content of different tomato types varied from 4 to 26 mg 100 (-1) g FW with chalconaringenin as the predominant compound comprising 35 to 71% of the total flavonoid content. The individual quantities of quercetin 3-O-(2''- O-beta-apiofuranosyl-6''- O-alpha-rhamnopyranosyl-beta-glucopyranoside) and phloretin 3',5'-di-C-beta-glucopyranoside was similar to that of rutin in several cultivars.

Molar absorptivities and reducing capacity of pyranoanthocyanins and other anthocyanins

To improve accuracy in the determination of anthocyanin purity and succeeding antioxidant capacity, 1H and 13C nuclear magnetic resonance spectroscopy have been combined with high-performance liquid chromatography (HPLC) equipped with a diode array detector and UV-vis spectroscopy in the analysis of anthocyanidin 3-glycosides and 5-carboxypyranoanthocyanidin 3-glycosides. The molar absoptivity (epsilon) values were found to be relatively similar, in contrast to previously reported literature values, and the average epsilon values for both anthocyanidin 3-monoglycosides and 5-carboxypyranoanthocyanidin 3-glycosides were proposed to be 22,000 and 23,000 in acidified aqueous and methanolic solutions, respectively. To assess the influence of structure on the potential antioxidant capacity of anthocyanins, the 3-glucosides of pelargonidin (1), cyanidin (2), peonidin (3), delphinidin (4), petunidin (5), malvidin (6), 5-carboxypyranopelargonidin (8), 5-carboxypyranocyanidin (9), 5-carboxypyranodelphinidin (11), 5-carboxypyranopetunidin (12), and 5-carboxypyranomalvidin (13) and the 3-galactosides of cyanidin (7) and 5-carboxypyranocyanidin (14) were examined by a ferric ion reducing antioxidant power (FRAP) assay. The reducing capacities of the individual anthocyanins were in the range of 0.9-5.2 micromol of Trolox equivalents/micromol. The two 5-carboxypyranoanthocyanins 11 and 9 and the four common anthocyanins 2, 4, 7, and 14, all possessing pyrogallol or catechol type of B rings, showed the highest antioxidant capacity measured by FRAP. However, the inclusion of the 5-hydroxyl in the D ring and just one oxygen substituent on the B ring in 8 diminished the reducing capacity considerably. Correspondingly, electrochemical behavior of 5-carboxypyranoanthocyanidin 3-glucosides and anthocyanidin 3-glucosides was derived using HPLC coupled to a coulometric array detector set from 100 to 800 mV in increments of 100 mV. The relative order of the reducing capacity of the various 5-carboxypyranoanthocyanidin 3-glucosides and anthocyanidin 3-glucosides were nearly alike, whether determined by coulometric array detection or FRAP.

Onions: a source of unique dietary flavonoids

Onion bulbs (Allium cepa L.) are among the richest sources of dietary flavonoids and contribute to a large extent to the overall intake of flavonoids. This review includes a compilation of the existing qualitative and quantitative information about flavonoids reported to occur in onion bulbs, including NMR spectroscopic evidence used for structural characterization. In addition, a summary is given to index onion cultivars according to their content of flavonoids measured as quercetin. Only compounds belonging to the flavonols, the anthocyanins, and the dihydroflavonols have been reported to occur in onion bulbs. Yellow onions contain 270-1187 mg of flavonols per kilogram of fresh weight (FW), whereas red onions contain 415-1917 mg of flavonols per kilogram of FW. Flavonols are the predominant pigments of onions. At least 25 different flavonols have been characterized, and quercetin derivatives are the most important ones in all onion cultivars. Their glycosyl moieties are almost exclusively glucose, which is mainly attached to the 4', 3, and/or 7-positions of the aglycones. Quercetin 4'-glucoside and quercetin 3,4'-diglucoside are in most cases reported as the main flavonols in recent literature. Analogous derivatives of kaempferol and isorhamnetin have been identified as minor pigments. Recent reports indicate that the outer dry layers of onion bulbs contain oligomeric structures of quercetin in addition to condensation products of quercetin and protocatechuic acid. The anthocyanins of red onions are mainly cyanidin glucosides acylated with malonic acid or nonacylated. Some of these pigments facilitate unique structural features like 4'-glycosylation and unusual substitution patterns of sugar moieties. Altogether at least 25 different anthocyanins have been reported from red onions, including two novel 5-carboxypyranocyanidin-derivatives. The quantitative content of anthocyanins in some red onion cultivars has been reported to be approximately 10% of the total flavonoid content or 39-240 mg kg (-1) FW. The dihydroflavonol taxifolin and its 3-, 7-, and 4'-glucosides have been identified in onions. Although the structural diversity of dihydroflavonols characterized from onions is restricted compared with the wide structural assortment of flavonols and anthocyanins identified, they may occur at high concentrations in some cultivars. From bulbs of the cultivar "Tropea", 5.9 mg of taxifolin 7-glucoside and 98.1 mg of taxifolin have been isolated per kilogram of FW.

Reactivity of anthocyanins and pyranoanthocyanins. Studies on aromatic hydrogen-deuterium exchange reactions in methanol

Reactivity studies involving anthocyanin structures and their equilibrium forms will lead to better understanding of the properties of these antioxidants. Hydrogen-deuterium (H --> D) exchange reactions at various sites of the 3-glucosides of delphinidin (1), petunidin (2), malvidin (3), and the corresponding 3-glucosides of carboxypyranodelphinidin (4), carboxypyranopetunidin (5), carboxypyranomalvidin (6), and the flavonol quercetin 3-O-(6-alpha-rhamnopyranosyl-beta-glucopyranoside)(7) have been examined at room temperature in pure CD 3OD and in CD 3OD acidified with CF 3CO 2D. The H --> D exchange rate constants of H-6 and H-8 of 2 determined from (1)H NMR integration data were found to be independent upon pigment concentration (up to 4 x 10 (-2) M) and trifluoroactic acid concentration (0-15%, v/v), respectively. This suggest that these reactions follow first-order kinetics and unexpectedly to be independent of the acid concentration. H-6 and H-8 of the flavylium cation A-rings of 1- 3, and in the corresponding hydrogens of the hemiketal forms, exchanged with half-lives of approximately 100 h ( 1) and approximately 50 h ( 2 and 3), respectively. The pyranoanthocyanins (4-6) experienced no H --> D exchange for the analogous hydrogens, but H --> D exchange of H-beta (H-4)(t 1/2 approximately 25 h) for these compounds was observed. Only H-8 underwent significant H --> D exchange in 7. It is concluded that a stabilization of the sigma-complexes, assumed to be the intermediates in the reactions, takes place for the common anthocyanins (1-3) contrary to the pyranoanthocyanins (4-6).

Proline 35 of human immunodeficiency virus type 1 (HIV-1) Vpr regulates the integrity of the N-terminal helix and the incorporation of Vpr into virus particles and supports the replication of R5-tropic HIV-1 in human lymphoid tissue ex vivo

Mutational analysis of the four conserved proline residues in human immunodeficiency virus type 1 (HIV-1) Vpr reveals that only Pro-35 is required for efficient replication of R5-tropic, but not of X4-tropic, viruses in human lymphoid tissue (HLT) cultivated ex vivo. While Vpr-mediated apoptosis and G(2) cell cycle arrest, as well as the expression and subcellular localization of Vpr, were independent, the capacity for encapsidation of Vpr into budding virions was dependent on Pro-35. (1)H nuclear magnetic resonance data suggest that mutation of Pro-35 causes a conformational change in the hydrophobic core of the molecule, whose integrity is required for the encapsidation of Vpr, and thus, Pro-35 supports the replication of R5-tropic HIV-1 in HLT.

Covalent anthocyanin-flavone dimer from leaves of Oxalis triangularis

The anthocyanin-flavone C-glycoside, (malvidin 3-O-(6(II)-O-alpha-rhamnopyranosyl(AIV)-beta-glucopyranoside(AII))-5-O-beta-glucopyranoside(AIII)) (apigenin 6-C-(2(II)-O-beta-glucopyranosyl(FIII)-beta-glucopyranoside(FII))) malonate(AV) (A(IV)-4-->A(V)-1, F(III)-6-->A(V)-3) (1), has been isolated from leaves of Oxalis triangularis A. St.-Hil. In the 1D (1)H NMR spectrum of 1 dissolved in CD(3)OD-CF(3)CO(2)D (95:5), MTFA, recorded 45 min after sample preparation, this covalently linked dimer occurred mainly as flavylium cation (38%) and two equilibrium forms assigned to be quinonoidal bases (54%), whereas only minor amounts of the hemiacetal forms were present. After five days storage at 300 K, the hemiacetals (39%) and flavylium cation (38%) constituted the main forms of 1. More simple anthocyanins are normally considered to be on the flavylium cation form in acidified deuterated methanol. The cross-peaks observed in NOESY NMR spectra of 1 indicated the presence of vertical 'pi-pi' stacking between the B-ring of the flavone unit and the A-ring of each of the two forms assigned to be quinonoidal bases. It was not possible to discriminate between inter- or intramolecular association mechanisms. The equilibria between the various forms of 1 were studied by two-dimensional NOESY and ROESY NMR spectroscopy. 2D HSQC-TOCSY NMR spectroscopy was among the methods used for characterization of the various forms.

Anthocyanin 3-galactosides from Cornus alba 'Sibirica' with glucosidation of the B-ring

The three anthocyanins, delphinidin 3-O-beta-galactopyranoside-3',5'-di-O-beta-glucopyranoside (1), delphinidin 3-O-beta-galactopyranoside-3'-O-beta-glucopyranoside (2) and cyanidin 3-O-beta-galactopyranoside-3'-O-beta-glucopyranoside (3), and the 3-O-beta-galactopyranosides of delphinidin (4) and cyanidin (5) were isolated from the bluish white berries and compound umbel of Siberian dogwood, Cornus alba 'Sibirica'. The ornamental autumn leaves and the characteristic purplish red bark of this variety were found to contain only pigment 5.

Characterization of hemiacetal forms of anthocyanidin 3-O-beta-glycopyranosides

The 3-O-beta-glucopyranosides of delphinidin, petunidin, and malvidin (1-3) and cyanidin 3-O-beta-galactopyranoside (4) dissolved in deuterated methanolic solutions without and with acid (5%, CF3COOD) were identified by homo- and heteronuclear NMR techniques. The hemiacetal forms of all the four anthocyanins were characterized as two epimeric 2-hydroxy-hemiacetals on the basis of assignments of both proton and carbon NMR signals together with chemical shift considerations. This is the first report of 13C NMR assignments of two epimeric anthocyanin hemiacetal forms. No 4-hydroxy-hemiacetal form was detected for any of the pigments. For each anthocyanin dissolved in deuterated methanol, the equilibrium between each of the two epimeric hemiacetals and the corresponding flavylium cation was confirmed by the observed positive exchange cross-peaks in the 2D 1H NOESY spectra. The molar proportions of the flavylium cation and the two hemiacetals of 1-4 in deuterated methanol were very similar for all pigments, even during storage for weeks. The majority of the anthocyanins reported to occur in fruits have the same or similar structures as 1-4. These pigments have been proposed to exist predominantly as hemiacetals in slightly acidic to neutral solvents, which is a relevant pH range in plants and in the human gastrointestinal tract.

Structural characterization and oligomerization of PB1-F2, a proapoptotic influenza A virus protein

Recently, a novel 87-amino acid influenza A virus protein with proapoptotic properties, PB1-F2, has been reported that originates from an alternative reading frame in the PB1 polymerase gene and is encoded in most known human influenza A virus isolates. Here we characterize the molecular structure of a biologically active synthetic version of the protein (sPB1-F2). Western blot analysis, chemical cross-linking, and NMR spectroscopy afforded direct evidence of the inherent tendency of sPB1-F2 to undergo oligomerization mediated by two distinct domains located in the N and C termini, respectively. CD and (1)H NMR spectroscopic analyses indicate that the stability of structured regions in the molecule clearly depends upon the hydrophobicity of the solvent. In aqueous solutions, the behavior of sPB1-F2 is typical of a largely random coil peptide that, however, adopts alpha-helical structure upon the addition of membrane mimetics. (1)H NMR analysis of three overlapping peptides afforded, for the first time, direct experimental evidence of the presence of a C-terminal region with strong alpha-helical propensity comprising amino acid residues Ile(55)-Lys(85) connected via an essentially random coil structure to a much weaker helix-like region, located in the N terminus between residues Trp(9) and Lys(20). The C-terminal helix is not a true amphipathic helix and is more compact than previously predicted. It corresponds to a positively charged region previously shown to include the mitochondrial targeting sequence of PB1-F2. The consequences of the strong oligomerization and helical propensities of the molecule are discussed and used to formulate a hypothetical model of its interaction with the mitochondrial membrane.

Preparative isolation and NMR characterization of carboxypyranoanthocyanins

Three pyranoanthocyanins, the 3-glucosides of 5-carboxypyranodelphinidin (2), 5-carboxypyranopetunidin (4), and 5-carboxypyranomalvidin (6), were produced by nucleophilic addition of pyruvic acid to a purified extract of black beans (Phaseolus vulgaris) containing a mixture of the 3-glucosides of delphinidin (1), petunidin (3), and malvidin (5). A Sephadex LH-20 column was used for preparative separation of both pyranoanthocyanins and anthocyanins. The optimum solvent used for isocratic separation was 20% methanol containing 0.5% trifluoroacetic acid. The chromatographic method applied on the pigment mixture yielded in a one-step separation pigments 1-6, with purities up to 98, 89, 99, 87, 55, and 81%, respectively. The structures of 2 and 4, which previously have been tentatively identified mainly by mass spectrometric data acquired from pigment mixtures in wine samples or modified blueberry extract, were confirmed in the present study by two-dimensional nuclear magnetic resonance spectroscopy.

Flavone C-glycosides from leaves of Oxalis triangularis

The flavone C-glycosides luteolin 6-C-(2''-O-beta-xylopyranosyl-beta-glucopyranoside) (1), apigenin 6-C-(2''-O-alpha-rhamnopyranosyl-beta-glucopyranoside) (2), apigenin 6-C-(2''-O-beta-xylopyranosyl-beta-glucopyranoside) (3), apigenin 6-C-(2''-O-(6'''-(E)-caffeoylglucoside)-beta-glucopyranoside) (4), and apigenin 6-C-(2''-O-(6'''-(E)-p-coumaroylglucoside)-beta-glucopyranoside) (5) have been isolated from the purple leaves of Oxalis triangularis. Compound 4 is new, while 5 has previously been isolated from Cucumis sativus after treatment with silicon and infection with Sphaerotheca fuliginea. Signal duplication in the NMR spectra of 2, 4, and 5 revealed the presence of rotameric conformers, created by rotational hindrance at the C(sp3) -C(sp2) glucosyl-flavone linkage in these flavone C-glycosides.

Solution structure of the human immunodeficiency virus type 1 p6 protein

The human immunodeficiency virus type 1 p6 protein represents a docking site for several cellular and viral binding factors and fulfills major roles in the formation of infectious viruses. To date, however, the structure of this 52-amino acid protein, by far the smallest lentiviral protein known, either in its mature form as free p6 or as the C-terminal part of the Pr55 Gag polyprotein has not been unraveled. We have explored the high resolution structure and folding of p6 by CD and NMR spectroscopy. Under membranous solution conditions, p6 can adopt a helix-flexible helix structure; a short helix-1 (amino acids 14-18) is connected to a pronounced helix-2 (amino acids 33-44) by a flexible hinge region. Thus, p6 can be subdivided into two distinct structural and functional domains; helix-2 perfectly defines the region that binds to the virus budding factor AIP-1/ALIX, indicating that this structure is required for interaction with the endosomal sorting complex required for transport. The PTAP motif at the N terminus, comprising the primary late assembly domain, which is crucial for interaction with another cellular budding factor, Tsg101, does not exhibit secondary structure. However, the adjacent helix-1 may play an indirect role in the specific complex formation between p6 and the binding groove in Tsg101. Moreover, binding studies by NMR demonstrate that helix-2, which also comprises the LXXLF motif required for incorporation of the human immunodeficiency virus type 1 accessory protein Vpr into budding virions, specifically interacts with the Vpr binding region, indicating that under the specific solution conditions used for structure analysis, p6 adopted a functional conformation.

Isolation and identification of flavonoids, including flavone rotamers, from the herbal drug 'Crataegi folium cum flore' (hawthorn)

Twelve flavonoids, including seven flavones, four flavonols and one flavanone, were isolated from methanolic extract of the herbal drug 'Crataegi folium cum flore' (hawthorn leaves and flowers) by a combination of CC (over Amberlite XAD-7 and Sephadex LH-20) and preparative HPLC. Their structures, including that of the novel flavonol 8-methoxykaempferol 3-O-(6"-malonyl-beta-glucopyranoside), were elucidated by homo- and heteronuclear NMR and electrospray/MS. The 1H- and 13C-NMR of all compounds, including rotameric pairs of five flavone C-glycosides, were assigned. The presence and relative proportion of each rotamer was shown by various NMR experiments, including two-dimensional nuclear Overhauser and exchange spectroscopy, to depend on solvent, linkage position and structure of the C-glycosyl substituent.

Acylated anthocyanins from leaves of Oxalis triangularis

The novel anthocyanins, malvidin 3-O-(6-O-(4-O-malonyl-alpha-rhamnopyranosyl)-beta-glucopyranoside)-5-O-beta-glucopyranoside (2), malvidin 3-O-(6-O-alpha-rhamnopyranosyl-beta-glucopyranoside)-5-O-(6-O-malonyl-beta-glucopyranoside) (3), malvidin 3-O-(6-O-(4-O-malonyl-alpha-rhamnopyranosyl)-beta-glucopyranoside)-5-O-(6-O-malonyl-beta-glucopyranoside) (4), malvidin 3-O-(6-O-(4-O-malonyl-alpha-rhamnopyranosyl)-beta-glucopyranoside) (5) and malvidin 3-O-(6-O-(Z)-p-coumaroyl-beta-glucopyranoside)-5-O-beta-glucopyranoside (6), in addition to the 3-O-(6-O-alpha-rhamnopyranosyl-beta-glucopyranoside)-5-O-beta-glucopyranoside (1) and the 3-O-(6-O-(E)-p-coumaroyl-beta-glucopyranoside)-5-O-beta-glucopyranoside (7) of malvidin have been isolated from purple leaves of Oxalis triangularis A. St.-Hil. In pigments 2, 4 and 5 a malonyl unit is linked to the rhamnose 4-position, which has not been reported previously for any anthocyanin before. The identifications were mainly based on 2D NMR spectroscopy and electrospray MS.

Dimeric anthocyanins from strawberry (Fragaria ananassa) consisting of pelargonidin 3-glucoside covalently linked to four flavan-3-ols

Flavanol-anthocyanin complexes were isolated by successive use of Amberlite XAD-7 chromatography, Sephadex LH-20 gel filtration and preparative HPLC from acidified, methanolic extract of strawberries (Fragaria ananassa Dutch.). These purple minor pigments were characterized by UV-Vis spectroscopy, 1D and 2D NMR techniques, and electrospray mass spectrometry to be catechin(4alpha --> 8)pelargonidin 3-O-beta-glucopyranoside (1), epicatechin(4alpha --> 8)pelargonidin 3-O-beta-glucopyranoside (2), afzelechin(4alpha --> 8)pelargonidin 3-O-beta-glucopyranoside (3) and epiafzelechin(4alpha --> 8)pelargonidin 3-O-beta-glucopyranoside (4). The stereochemistry at the 3- and 4-positions of the flavan-3-ol units was based on assumption of R-configuration at C-2. Each of the four pigments occurred in the NMR solvent as a pair of rotamers. Proved by cross-peaks in the 1H-1H NOESY NMR spectra of 1, 2 and 4, the two conformations within each rotameric pair were in equilibrium with each other. Even though 1 and 2 are based on a different aglycone, their structures may be similar to tentatively identified pigments, which have been assumed to contribute to the colour of red wines.

Anthocyanin from strawberry (Fragaria ananassa) with the novel aglycone, 5-carboxypyranopelargonidin

An anthocyanin, 1, with the novel 4-substituted aglycone, 5-carboxypyranopelargonidin, was isolated in small amounts from the acidified, methanolic extract of strawberries, Fragaria ananassa Duch., by preparative HPLC after purification by partition against ethyl acetate, Amberlite XAD-7 and Sephadex LH-20 column chromatography. It was identified mainly by 2D NMR spectroscopy and electrospray LC-MS as the 3-O-beta-glucopyranoside of 5-carboxy-2-(4-hydroxyphenyl)-3,8-dihydroxy-pyrano[4,3,2-de]-1-benzopyrylium, an anthocyanidin which is homologous to 5-carboxypyranomalvidin (vitisidin A) reported in red wines and 5-carboxypyranocyanidin recently isolated from red onions. By comparison of UV-Vis absorption spectra, 1 showed in contrast to 2, pelargonidin 3-O-beta-glucopyranoside, a local absorption peak around 360 nm, a hypsochromic shift (8 nm) of the visible absorption maximum, and lack of a distinct UV absorption peak around 280 nm. The similarities between the absorption spectra of 1 in various acidic and neutral buffer solutions implied restricted formation of the instable colourless equilibrium forms, which are typical for most anthocyanins in weakly acidic solutions. The molar absorptivity (epsilon) of 1 varied little with pH contrary to similar values of for instance the major anthocyanin in strawberry, 2. However, 2 revealed higher epsilon-values than 1 at all pH values except 5.1. At pH 5.1, the epsilon-value of 1 (6250) was nearly four times the corresponding value of 2 (1720), which showed the potential of 5-carboxypyranopelargonidin derivatives as colorants in solutions with pH around 5. The colours of 1 and 2 in buffered solutions with pH 1.1 and pH 6.9 have been described by the CIELAB coordinates h(ab) (hue angle), C* (chroma), and L* (lightness).

Anthocyanins with 4'-glucosidation from red onion, Allium cepa

The anthocyanins, cyanidin 3-O-(3"-O-beta-glucopyranosyl-6"-O-malonyl-beta-glucopyranoside)-4'-O-beta-glucopyranoside, cyanidin 7-O-(3"-O-beta-glucopyranosyl-6"-O-malonyl-beta-glucopyranoside)-4'-O-beta-glucopyranoside, cyanidin 3,4'-di-O-beta-glucopyranoside, cyanidin 4'-O-beta-glucoside, peonidin 3-O-(6"-O-malonyl-beta-glucopyranoside)-5-O-beta-glucopyranoside and peonidin 3-O-(6"-O-malonyl-beta-glucopyranoside) have been isolated in minor amounts from pigmented scales of red onion, Allium cepa, in addition to six known anthocyanins. The structures were established mainly by extensive use of 2D NMR spectroscopy and electrospray LC-MS. With exception of cyanidin 4'-glucoside and cyanidin 3,4'-diglucoside reported from Hibiscus esculentus with inadequate documentation, this is the first identification of anthocyanins with 4'-glycosidation. Compared to cyanidin 3-glycosides the cyanidin 4'-glucoside derivatives showed hypsochromic shifts of visible lambda(max) and hyperchromic effects on wavelengths around 440 nm, similar to pelargonidin 3-glycosides.

Structural characterization of the HIV-1 Vpr N terminus: evidence of cis/trans-proline isomerism

The 96-residue human immunodeficiency virus (HIV) accessory protein Vpr serves manifold functions in the retroviral life cycle including augmentation of viral replication in non-dividing host cells, induction of G2 cell cycle arrest, and modulation of HIV-induced apoptosis. Using a combination of dynamic light scattering, circular dichroism, and NMR spectroscopy the N terminus of Vpr is shown to be a unique domain of the molecule that behaves differently from the C-terminal domain in terms of self-association and secondary structure folding. Interestingly, the four highly conserved proline residues in the N terminus are predicted to have a high propensity for cis/trans isomerism. Thus the high resolution structure and folding of a synthetic N-terminal peptide (Vpr1-40) and smaller fragments thereof have been investigated. 1H NMR data indicate Vpr1-40 possesses helical structure between residues 17-32, and for the first time, this helix, which is bound by proline residues, was observed even in aqueous solution devoid of any detergent supplements. In addition, NMR data revealed that all of the proline residues undergo a cis/ trans isomerism to such an extent that approximately 40% of all Vpr molecules possess at least one proline in a cis conformation. This phenomenon of cis/trans isomerism, which is unprecedented for HIV-1 Vpr, not only provides an explanation for the molecular heterogeneity observed in the full-length molecule but also indicates that in vivo the folding and function of Vpr should depend on a cis/trans-proline isomerase activity, particularly as two of the proline residues in positions 14 and 35 show considerable amounts of cis isomers. This prediction correlates well with our recent observation (Zander, K., Sherman, M. P., Tessmer, U., Bruns, K., Wray, V., Prechtel, A. T., Schubert, E., Henklein, P., Luban, J., Neidleman, J., Greene, W. C., and Schubert, U. (2003) J. Biol. Chem. 278, 43170-43181) of a functional interaction between the major cellular isomerase cyclophilin A and Vpr, both of which are incorporated into HIV-1 virions.