Expanding the Druggable Proteome with Chemical Biology – Best Poster Awards

The 2020 conference season at the EMBL Advanced Training Centre kicked off with the EMBL Conference: Expanding the Druggable Proteome with Chemical Biology (5 – 7 February 2020). Meet the three poster prize winners from the conference – Patrick Zanon, Enric Ros and Rens de Vries.

Identification of novel antibiotic targets using covalent inhibitors and residue-specific proteomics

PHOTO: Patrick Zanon

Authors: Patrick Zanon (1), Stephan Hacker (1)

Bacterial resistance towards all marketed antibiotics poses an imminent threat to global health. In order to overcome this antibiotic crisis, drugs with novel mechanisms-of-action are desperately needed. Covalent inhibitors are especially promising in this regard as they are already prevalent as antibiotics (e.g. β-lactams and fosfomycin), allow targeting protein pockets that are hard to address with non-covalent interactions alone and hold the promise to overcome some mechanisms of resistance development.[1] Furthermore, covalent inhibitors are uniquely suited to identify new binding pockets on proteins using residue-specific proteomics and in this way to broaden the scope of targetable protein targets.
The vast majority of covalent inhibitors so far either hijack the enzymatic activity of the protein by modification of catalytic serines and tyrosines or address cysteines through their inherent outstanding nucleophilicity. Nevertheless, the number of potentially addressable proteins in the bacterial proteome is significantly limited by the requirement for these amino acids to be present in target proteins. By developing electrophilic groups that are selective for other amino acids (e.g. lysine), we strive to expand the number of exploitable interaction sites for covalent inhibitors in the bacterial proteome. Furthermore, to assess the reactivity and selectivity of covalent inhibitors and to streamline the discovery of novel antibiotic targets, we develop new methods for residue-specific activity-based protein profiling.[2,3] In this way, we are convinced, that we will be able to make important contributions to overcome the antibiotic crisis.

References:
[1] R. A. Bauer, Drug Discov. Today 2015, 20, 1061–1073.
[2] K. M. Backus et al., Nature 2016, 534, 570.
[3] P. R. A. Zanon, L. Lewald, S. M. Hacker Angew. Chem. Int. Ed., doi: 10.1002/anie.201912075.

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(1) Technical University of Munich, Germany


Incorporating 1,2,4,5-tetrazines into proteins: A method for targeted drug release

PHOTO: Enric Ros

Authors: Enric Ros (1), Antoni Riera (1), Lluís Ribas de Pouplana (1)

Bioorthogonal reactions, namely reactions that can take place under biocompatible conditions, are having a major impact in the development of new research tools and novel therapeutic strategies. In the latter case, the discovery of the reaction commonly referred to as “click-to-release” (CtR), which triggers the liberation of a given cargo (normally a drug or a fluorophore), has led to several applications in drug delivery. This reaction happens between a 1,2,4,5-Tetrazine (Tz) fragment and certain alkenes or alkynes and, in order to achieve drug delivery specifically at the site of action, one of the two reactant counterparts should be conjugated to a biomolecule acting as a carrier, ideally a protein.
We have synthetized the previously unreported 3-bromo-1,2,4,5-tetrazine and used its excellent reactivity to attain chemoselective protein labelling onto lysines. Due to the chemical features of the formed amino-Tz. The resulting labelled lysines can undergo fast CtR reactions with trans-cyclooctenes, thereby releasing a desired cargo under physiological conditions. To showcase the applicability of this approach, we have labelled the monoclonal antibody Trastuzumab (anti-Her2) and demonstrated the specific release of the cytotoxic drug doxorubicin upon reaction in a mammalian cell culture context, resulting in a decrease in cell viability.
Additionally, we have also used 3-bromo-1,2,4,5-tetrazine to synthetize an amino-Tz containing non-natural amino acid and used it to achieve protein labelling through its genetic incorporation by amber codon suppression in Escherichia coli. The resulting site-selectively labelled proteins can also trigger fast, high yielding CtR reactions.
To summarize, we have successfully applied a new compound, 3-bromo-1,2,4,5-tetrazine, as a reagent to achieve either chemoselective or site selective protein labelling. We have applied the bioconjugated proteins to demonstrate their potential use for targeted drug delivery in a relevant cellular model, opening new therapeutically useful methodologies.

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(1) IRB Barcelona, Spain


Modulation of nuclear receptors through ligand architecture

PHOTO: Rens de Vries

Authors: Rens de Vries (1), Femke Meijer (1), Luc Brunsveld (1)

Nuclear receptors (NRs) have been one of the primary drug targets over the last decades for their ability to regulate gene expression. The traditional approach of modulating NRs is to design small synthetic molecules that interact with the ligand-binding domain (LBD) of the NR. Ligands can thereby either enhance or inhibit gene transcription. Apart from the effects on transcription, recent research shows that minor changes in the ligand scaffold can have a significant impact on the behavior of the NR. In this research, we show how small-molecules can change both the dimerization behavior of NRs and the recruitment of allosteric modulators.
The Retinoic X Receptor α (RXRα) is known as a master regulator among NRs through its ability to heterodimerize with, and thereby modulate, other NRs. We show, using a novel NanoBIT complexation assay, that small directed changes in the RXR ligand scaffold can lead to selective formation of specific hetero- and homodimers. Using our structural data and focused compound library, a model was developed to help to understand this effect of the ligand. This information can serve as a blueprint to design small-molecules that selectively target specific NRs via RXR. This makes RXR as an exciting and versatile target for NR modulation, especially when classical modulation of the partner NR is not possible.
Recently, small-molecules have been found to bind to allosteric sites of NRs. Allosteric ligands are of interest since they do not compete with the endogenous ligand of the NR and often shown an increased selectivity towards their target. We show, using X-ray crystallography and biochemical assays, that there is communication between orthosteric and allosteric ligands in the RAR-related orphan receptor γ t (RORγt). We successfully solved eleven new ternary crystal structures of RORγt in the presence of both orthosteric and allosteric ligands. These structures mechanistically show how binding of the orthosteric ligand leads to positive cooperative binding of the allosteric ligand.

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(1) Eindhoven University of Technology, The Netherlands


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Best Poster Awards – Target Validation Using Genomics and Informatics

Meet Giovanni Spirito and Borja Gomez Ramos – the two poster prize winners at the recent EMBL – Wellcome Genome Campus Conference: Target Validation Using Genomics and Informatics (8 – 10 Dec 2019).

Identification and prioritization of candidate causal genomic variations from individuals affected by ASD

PHOTO: Giovanni Spirito

Authors: Giovanni Spirito (1), Diego Vozzi (2), Martina Servetti (3), Margherita Lerone (3), Maria Teresa Divizia (3), Giulia Rosti (3), Livia Pisciotta (4), Lino Nobili (4), Irene Serio (4), Stefano Gustincich (2), Remo Sanges (1)

Next generation sequencing (NGS) technologies enabled the extensive study of the genomics underlying human diseases. Namely whole exome sequencing (WES) represents a cost-efficient method which can lead to the detection of multiple classes of genomic variants and the discovery of novel disease-associated genes. One of the drawbacks of this approach however, is the large number of genomic variants detected in each analysis. Automated variant prioritization strategies are therefore required. This is particularly important in the case of complex disease such as ASD, whose genetic etiology is still poorly understood. To this aim we built a custom computational framework capable, from raw WES data, to automatically detect four classes of genomic variants (SNPs, indels, copy number variants and short tandem repeat variants) and prioritize them in regards to their relevance to a specific phenotype. We tested this framework on a selection of 29 trios including probands affected by severe and undiagnosed rare phenotypes and a small cohort of 10 trios all featuring healthy parents and one offspring affected by autism spectrum disorder (ASD). We were able to successfully detect rare and de novo high penetrance variants which have been validated and confirmed as causative among the undiagnosed probands. In the specific case of the ASD cohort we could highlight several genes which are not implicated in autism susceptibility, but nevertheless whose connections to genes relevant for ASD could suggest a possible involvement in the phenotype. Furthermore, our approach enabled us to detect several instances characterized by the presence of multiple candidate variants within genes belonging to the same canonical pathway in one proband. Our workflow allows to detect and prioritize multiple classes of genomic variants in order to both highlight rare high penetrance disease-causative mutation, and possibly reconstruct the genomics at the basis of complex ASD phenotypes.

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(1) SISSA, Italy, (2) IIT, Italy, (3) Gaslini Institute, Italy, (4) University of Genova, Italy


Omics data integration for the identification of cell-type-specific gene regulatory networks and regulatory variants in Parkinson’s disease

PHOTO: Borja Gomez Ramos

Authors: Borja Gomez Ramos (1,2), Jochen Ohnmacht (1,2), Nikola de Lange (2), Aurélien Ginolhac (1), Aleksandar Rakovic (5), Christine Klein (5), Roland Krause (2) , Marcel H. Schulz (6), Thomas Sauter (1), Rejko Krüger (2,3,4) and Lasse Sinkkonen (1)

Genome-Wide Association Studies (GWAS) have identified many variants associated with different diseases. However, it is still a challenge to make sense of this data as the majority of genetic variants are located in non-coding regions, complicating the understanding of their functionality. In the last few years, it has been found that non-coding genetic variants concentrate in regulatory regions in the genome, which are cell type and cell-stage specific. In this project, we seek to identify functional Parkinson’s disease GWAS non-coding genetic variants that could make carriers more prone to developing PD. To do so, we are using induced pluripotent stem cell (iPSC) technology to differentiate somatic cells into midbrain dopaminergic (mDA) neurons, astrocytes and microglia. Assessing their chromatin accessibility, active chromatin regions and transcriptome, we can identify crucial regulatory regions in the genome, key transcription factors and derive the gene regulatory networks for the three different cell types. Then, we will map the non-coding genetic variants to the different regulatory regions and predict their effect in silico for the subsequent validation in vitro. This innovative approach will also identify novel factors controlling cell fate and cell identity.

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(1) Life Sciences Research Unit, University of Luxembourg, Luxembourg, (2) Luxembourg Centre for Systems Biomedicine (LCSB), University of Luxembourg, Luxembourg, (3) Centre Hospitalier de Luxembourg (CHL), Luxembourg, (4) Luxembourg Institute of Health (LIH), Luxembourg, (5) Institute of Neurogenetics, University of Lübeck, Germany, (6) Institute for Cardiovascular Regeneration, Uniklinikum and Goethe University Frankfurt, Germany


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Best Poster Awards – Cancer Genomics

The 4th EMBL Conference: Cancer Genomics (4 – 6 November 2019) brought together over 240 scientists in the field of cancer research to present the latest findings in cancer functional genomics, systems biology, cancer immunogenomics and epigenomics, as well as their translation and clinical impact.

123 posters were presented at the two poster sessions, out of which two were selected as the winners by popular vote. 

Infinite sites violations during tumour evolution reveal local mutational determinants

Jonas Demeulemeester is a postdoctoral researcher at the Francis Crick Insitute in UK. PHOTO: Jonas Demeulemeester

Authors: Jonas Demeulemeester (1), Stefan C. Dentro (2), Moritz Gerstung (2), Peter Van Loo (1)

The infinite sites model of molecular evolution requires that every base in the genome is mutated at most once. It is a cornerstone of (tumour) phylogenetic analysis, and is often implied when calling, phasing and interpreting variants or studying the mutational landscape as a whole. It is unclear however, whether this assumption holds in practice for bulk tumour samples. Here we provide frameworks to model and detect infinite sites violations, identifying 24,459 in total, including 6 candidate biallelic driver events, in 700 bulk tumour samples (26.3%) from the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes project. Violations generally occur at mutational hotspots and their frequency and type can accurately be predicted from the overall mutation spectrum. In melanoma, their local sequence context evidences how not only ETS, but also NFAT-family transcription factor binding creates hotspots for UV-induced cyclobutane pyrimidine dimer formation. In colorectal adenocarcinoma, violations reveal hypermutable special cases of the trinucleotide mutational contexts identified in POLE-mutant tumours. Taken together, we reveal the infinite sites model breaks down at the bulk level for a considerable fraction of tumours. These results warrant a careful evaluation of current pipelines relying on the validity of the infinite sites assumption, especially when scaling up to larger sets of mutations and lineages in the future.

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(1) The Francis Crick Institute, United Kingdom, (2) EMBL-EBI, United Kingdom


The other award-winning poster was:

Understanding the early impact of activating PIK3CA mutation on cellular and genetic heterogeneity presented by Evelyn Lau, UCL Cancer Institute, United Kingdom


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Best Poster Awards – The Non-Coding Genome

Taking place for the third time,  the EMBO|EMBL Symposium: The Non-Coding Genome (16 – 19 October 2019) brought together 305 RNA experts to discuss the roles of non-coding RNAs in both prokaryotes and eukaryotes, gene regulation and function. 

A total of 189 posters were presented, from which two were singled out as the winners by popular vote.

Characterization of the genomic and splicing features of long non-coding RNAs using bioinformatics approaches

Monah Abou Alezz is a Ph.D student in genetics, molecular and cellular biology at the University of Pavia, Italy. PHOTO: Monah Abou Alezz

Authors: Monah Abou Alezz, Ludovica Celli, Giulia Belotti, Silvia Bione, Institute of Molecular Genetics L. L Cavalli-Sforza – National Research Council, Italy

Recent developments in deep sequencing approaches have simulated the continuous discovery of a significantly large number of novel long non-coding RNA (lncRNA) genes loci in the genomes. Long non-coding RNAs are recognized as a new class of regulatory molecules despite very little is known about their functions in the cellular processes. Due to their overall low expression level and tissue-specificity, the identification and annotation of lncRNA genes still remains challenging. The characterization of lncRNAs’ features is crucial to understand and get functional insights on their mechanisms of action. We exploited recent annotations by the GENCODE compendium to characterize the genomic and splicing features of long non-coding genes, in comparison to protein-coding ones, in the human and mouse genome by using bioinformatics approaches. Our analysis highlighted differences between the two classes of genes in terms of gene architecture regarding exons and introns length, GC-content, and the combinatorial patterns of chromatin marks and states. Moreover, significant differences in the splice sites usage were observed between long non-coding and protein-coding genes. While the frequency of non-canonical GC-AG splice junctions represents about 0.8% of total splice sites in protein-coding genes, we identified a remarkable enrichment of the GC-AG splice sites in long non-coding genes, both in human (3.0%) and mouse (1.9%). In addition, we identified peculiar characteristics of the GC-AG introns in terms of donor and acceptor splice sites strength, poly-pyrimidine tract, intron length, and a positional bias of GC-AG junctions being enriched in the first intron. Genes containing at least one GC-AG intron were found conserved in many species across large evolutionary distances, more prone to alternative splicing and a functional analysis pointed toward their enrichment in specific biological processes such as
DNA repair.

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MirGeneDB 2.0: The metazoan microRNA complement

Bastian Fromm is a Senior Researcher at Science for Life Laboratory, Stockholm University, Sweden. PHOTO: Bastian Fromm

Authors: Bastian Fromm (1), Diana Domanska (2), Eirik Hoye (3), Vladimir Ovchinnikov (4), Wenjing Kang (5), Ernesto Aparicio-Puerta (6), Morten Johansen (7), Kjersti Flatmark (3), Anthony Mathelier (8), Hovig
Eivind (3), Michael Hackenberg (6), Marc Friedländer (5), Kevin Peterson (9)

Non-coding RNAs (ncRNA) have gained substantial attention due to their roles in human disorders and animal development. microRNAs (miRNAs) are unique within this class as they are the only ncRNAs with individual gene sequences conserved across the animal kingdom. Bona fide miRNAs can be clearly distinguished from the myriad small RNAs generated in cells by a set of unique criteria. Unfortunately, recognition and utilization of these clear and mechanistically well understood features is not a  common practice. We addressed this by extensively expanding our curated miRNA gene database MirGeneDB to 45 organisms that represent the breadth of Metazoa. By consistently annotating and naming more than 11,000 miRNA genes in these organisms, we show that previous miRNA annotations contained not only many false positives, but surprisingly many false negatives as well. Indeed, curated miRNA complements of closely related organisms are very similar and can be used to reconstruct evolution of miRNA genes, families and biogenesis across more than 1 billion years of evolution. MirGeneDB represents a robust platform for providing deeper and more significant insights into the biology of miRNAs, possible sources of mis-regulation, and evolutionary mechanisms. MirGeneDB is publicly and freely available under http://mirgenedb.org/.

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Fromm, B. et al. MirGeneDB 2.0: the metazoan microRNA complement. Nucleic Acids Research, gkz885, (2019), https://doi.org/10.1093/nar/gkz885

(1) Science for Life Laboratory, Sweden
(2) Department of Informatics, University of Oslo, Oslo, Norway
(3) Department of Tumor Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
(4) School of Life Sciences, Faculty of Health and Life Sciences, University of Nottingham, United Kingdom
(5) Stockholm University, SciLifeLab, Sweden
(6) Department of Genetics, Faculty of Sciences, University of Granada, Granada, Spain
(7) Institute for Medical Informatics, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
(8) Centre for Molecular Medicine Norway (NCMM), Nordic EMBL Partnership, University of Oslo, Oslo, Norway
(9) Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire, United States of America


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Best Poster Awards – EMBO Workshop: Tools for Structural Biology of Membrane Proteins

183 researchers convened at the Centre for Structural Systems Biology (CSSB) in Hamburg, Germany, for the recent EMBO Workshop: Tools for Structural Biology of Membrane Proteins (7 – 9 October 2019) to present and discuss new technologies and approaches applied in studying membrane protein structure, dynamics and functions.

Out of the 82 posters presented, 6 were awarded a poster prize based on popular vote. Here we present the poster abstracts of four of the winners.

Structural insights into the role of the conserved ATPase component, EccC, in the mycobacterial T7SS

Katherine Beckham is a postdoctoral fellow in Matthias Wilmanns’ group at EMBL Hamburg. PHOTO: Katherine Beckham

Authors: Katherine Beckham (1), Luciano Ciccarelli (1), Mandy Rettel (2), Mikhail Savitski (2), Jan Kosinski (1), Annabel
Parret (1), Matthias Wilmanns (1)

Mycobacteria have a unique membrane structure with a complex hydrophobic outer-membrane rich in mycolic acids. To transport substances across this impermeable barrier, mycobacteria rely on a highly specialised translocation machinery – the Type VII secretion system (T7SS). Pathogenic mycobacteria encode up to five distinct T7SSs ESX-1 to 5 [1]. Our previous work characterised the structure of the of the inner-membrane complex of the ESX-5 T7SS from Mycobacterium xenopi using negative stain electron microscopy, revealing a hexameric 1.8 MDa complex comprising the four conserved core components: EccB5, EccC5, EccD5 and EccE5 [2]. The large cytosolic domain of EccC5, an FtsK/SpoE-like ATPase, is absent in our current EM map due to its conformational flexibility, which may be required to accommodate a range of protein substrates. Our current work aims to understand the role of EccC5 in secretion. In isolation this component can oligomerise into a hexameric ring-like conformation, as observed for other ATPases in this family. In addition, chemical cross-linking of the ESX-5 complex coupled with mass spectrometry (XL-MS) supports the oligomerisation of EccC5 in the secretion complex, suggesting that it may form a channel or ‘translocation tunnel’. Thus, we propose that EccC5 may exist in two conformational states: an extended, flexible monomeric state and a more compact hexameric state. Using an integrative structural biology approach, we are combining structures of isolated proteins derived from X-ray crystallography and electron microscopy studies with XL-MS data. Together these data aim to further elucidate the secretion pathway across the mycobacterial cell envelope.

References:
[1] Houben, E. N. G., et al. Take five — Type VII secretion systems of Mycobacteria. Biochim. Biophys. Acta – Mol. Cell Res.1843, 1707–1716 (2014).
[2] Beckham, K. S. H. et al. Structure of the mycobacterial ESX-5 type VII secretion system membrane complex by single-particle analysis. Nat. Microbiol.2, 17047 (2017).

(1) EMBL Hamburg, Germany, (2) EMBL Heidelberg, Germany

Poster currently not available


Dissection of protonation sites for antibacterial recognition and transport in QacA, a multidrug efflux transporter

Puja Majumder is a Ph.D student at the Indian Institute of Science. PHOTO: Puja Majumder

Authors: Puja Majumder (1), Shashank Khare (1), Arunabh Athreya (1), Nazia Hussain (1), Ashutosh Gulati (2), Aravind Penmatsa (1)

Emergence of multidrug-resistance poses serious threat to the society. One of the effective way by which bacteria gain drug resistance is through active efflux of antibiotics and other antibacterial compounds using multidrug efflux transporters. Among the battery of efflux pumps present in pathogenic bacteria, our work is focused on QacA, a drug-proton anitiporter (DHA) with 14-transmembrane helices that provide resistance to methicillin resistant Staphylococcus aureus (MRSA) strain, with homologs present in other pathogenic organisms. QacA is a highly promiscuous transporter, capable of effluxing diverse array of monovalent and divalent cationic antibacterial compounds and dyes. This study using a homology model, dissects the role of six protonatable residues present in the transport vestibule of QacA. Systematic mutagenesis resulted in identification of D34 (TM1) and E407 (TM13) as crucial residues and D323 (TM10) and D411 (TM13) as conditional residues needed for transport process of QacA. Whole cells, inside-out vesicles, substrate-induced proton release and microscale thermophoresis based assays were used to investigate the transport and binding properties of the transporter and its mutants. The activity of purified protein was checked with reconstituted QacA in a proteoliposome using substrate-induced proton transport assay. We identify two sites, D34 and D411 playing vital role in recognition of most of the substrates tested while E407 facilitates substrate efflux as a protonation site. It was also observed that E407 has an additional role as a recognition site for the transport of dequalinium, a divalent quaternary ammonium compound. These observations rationalize the promiscuity at the residue level of QacA for diverse substrates. The study identifies the role of acidic residues in QacA with implications for substrate recognition, promiscuity and processive transport in multidrug efflux transporters, related to QacA.

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(1) Indian Institute of Science, India, (2) Stockholm University, Sweden


Biophysical analysis of circularized MSP nanodiscs for structural studies

Melina Daniilidis is a Ph.D student in Prof. Dr. Franz Hagn’s group at the Bavarian NMR Center (BNMRZ) of the Technical University of Munich. PHOTO: Melina Daniilidis

Authors: Melina Daniilidis (1), Ralf Stehle (1), Franz Hagn (1,2)

Structure and dynamics of membrane proteins are crucial aspects for understanding functional properties of this protein class. Unfortunately, stabilizing them in their isolated form is still difficult. By incorporating membrane proteins into nanodiscs, they can be studied in a native-like
environment using biochemical and structural methods. However, thermal and long-term stability of small nanodiscs limit these studies and make it difficult to carry out nuclear magnetic resonance spectroscopy (NMR) measurements at elevated temperatures. Circularized membrane scaffold proteins (MSPs) produced via split-inteins have been shown to be more stable and homogenous than their linear counterparts. However, their biophysical properties, as well as suitability for membrane protein insertion and structural studies have not yet been assessed in a systematic manner. Thus, we examined circular and linear nanodiscs of varying size using several biophysical methods. An important issue for NMR structural studies is that the size and shape of circular nanodiscs do not expand above the phase transition temperature, increasing their homogeneity and reducing their size as compared to linear nanodiscs at high temperatures. 1H,15N-TROSY experiments could demonstrate that circular MSP1D1 nanodiscs with incorporated VDAC-1 are stable at higher temperatures, making it possible to obtain high-resolution NMR spectra of superior quality. Furthermore, NMR relaxation experiments were carried out to compare rotational correlation times of VDAC-1 in circular and linear nanodiscs, respectively. Despite the higher molecular weight, the circular nanodiscs showed lower rotational correlation times, which corroborated the biophysical results on the temperature-dependecy of the nanodisc diameter and homogeneity. The presented data demonstrate that these very stable circularized MSPs are well applicable to the study of membrane proteins in a lipid environment by NMR, but also other structural methods like electron microscopy.

(1) Technical University of Munich, Germany, (2) Helmholtz Zentrum München, Germany

Poster currently not available


Reconstitution of the activity of RND efflux pumps into proteoliposomes

Dhenesh Puvanendran is a Ph.D student at the Institute of Physical and Chemical Biology in Paris, France. PHOTO: Dhenesh Puvanendran

Authors: Dhenesh Puvanendran, Quentin Cece, Martin Picard, IBPC, France

Efflux pumps are the major systems in bacterial resistance against antibiotics. They are classified by the energy needed to be active (ATP hydrolysis or ion counter-transport). Efflux pumps from the RND (Resistance, Nodulation, and cell Division) family use a proton gradient to be active and are composed of three proteins: a membrane fusion protein (MFP) and a transporter (RND) in the inner membrane, and an Outer Membrane Factor (OMF) localized in the outer membrane. We focus on the MexA-MexB-OprM efflux pump from Pseudomonas aeruginosa.The overall goal of my research is to measure in vitro the velocity of transport by efflux pumps. To that end, we reconstitute MexA and MexB as one population of proteoliposome, and OprM as another population of proteoliposome. The whole tripartite pump forms upon association of the respective populations of liposomes. The proof of concept of this method has already been described, leading to a qualitative monitoring of transport. We now work at defining a reconstitution procedure amenable to now quantify the rate of transport. To do so we take extreme care to precisely determine the efficiency of protein reconstitution and the type of lipids component used to perform liposomes. I will present the roadmap towards the rational, step-by-step, reconstitution of the MexA-MexB-OprM efflux pump as well as the methodologies that are undertaken to measure the velocity of transport, and possible perspectives regarding the screening of efflux pump inhibitors.

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The other award-winning posters are:

Novel antigen-binding chimeric proteins as tolls in crystallography and cryo-EM of membrane proteins presented by Thomasz Uchanski, Vrije Universiteit Brussel, Belgium

Cryo-Electron tomography of synaptic vesicle fusion junctions presented by Lucy Ginger, MRC Laboratory of Molecular Biology, United Kingdom


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