10:00

Dr. Kira J. Weissman

Biopôle de l'Université de Lorraine, Campus Biologie Santé, Nancy

Deciphering nature’s molecular-scale assembly lines

The discovery in the 1990s of the modular (assembly line) organization of certain polyketide synthases (PKSs) inspired attempts to genetically engineering the mega-enzymes to produce polyketide analogues of clinical value. However, despite decades of effort, success remains hampered by our limited understanding of how modular PKSs function. Work in our laboratory aims to facilitate PKS synthetic biology by establishing key structure-function relationships for PKS multienzymes using an integrated structural biology approach. We in addition apply our insights to generating new-to-nature polyketide derivatives. In this seminar, I will present a few highlights of our recent work in these areas.

Selected publications

• Davison J, Dorival J, Rabeharindranto H, Mazon H, Chagot B*, Gruez A* & Weissman KJ* (2014) Insights into the function of trans-AT polyketide synthases from the SAXS structure of a complete module. Chem Sci 5, 3081–3095
• Dorival J, Annaval T, Risser F, Collin S, Roblin P, Jacob C, Gruez A*, Chagot B* & Weissman KJ* (2016) Characterization of intersubunit communication in the virginiamycin trans-acyl transferase polyketide synthase. J Am Chem Soc 138, 4155–4167
• Dorival J, Risser F, Jacob C, Collin S, Dräeger G, Paris C, Chagot B, Kirschning A, Gruez A* & Weissman KJ* (2018) Insights into a dual function amide oxidase/macrocyclase from lankacidin biosynthesis. Nat Commun 9, 3988
• Risser F, Collin S, Dos Santos-Morais R, Gruez A*, Chagot B* & Weissman KJ* (2020) Towards improved understanding of intersubunit interactions in modular polyketide biosynthesis: docking in the enacyloxin IIa polyketide synthase. J Struct Biol In press. doi: 10.1016/j.jsb.2020.107581
• Massicard J-M, Soligot C, Weissman KJ* & Jacob C* (2020) Manipulating polyketide stereochemistry by exchange of polyketide synthase modules. Chem Commun Provisionally accepted.

10:40

Valérie Biou

Laboratoire de Biologie Physico-Chimique des Protéines Membranaires, Institut de Biologie Physico-Chimique, Paris

Cryo-EM structures of heme import complexes from S. marcescens

Gram-negative bacteria adapt to their environment by responding to external stimuli via signal transduction pathways. This results in gene expression to increase nutrient uptake and/or emission of virulence factors. Heme import in particular uses two-membrane spanning complexes involving TonB-like proteins. The transport is energised via a proton-motive-force driven complex located in the inner membrane composed of ExbB that assembles with two other proteins: a one-transmembrane domain protein with a periplasmic domain called ExbD and TonB analog HasB.

During this seminar, I will present the cryo-EM structures of ExbB and ExbB-ExbD from Serratia marcescens, an opportunistic pathogen, at 3.2 and 3.9Å respectively. The structures disclose the interactions between protein and lipids, and the contacts between ExbB and ExbD.

Selected references

• Jabrani, A., Makamte, S., Moreau, E., Gharbi, Y., Plessis, A., Bruzzone, L., Sanial, M., and Biou, V. (2017). Biophysical characterisation of the novel zinc binding property in Suppressor of Fused. Sci Rep 7, 11139
• Royes Mir, J., Biou, V., Dautin, N., Tribet, C., and Miroux, B. (2020). Intracellular Membranes: Conserved Mechanisms of Formation and Regulation Throughout Evolution. Preprints. DOI 10.20944/preprints202003.0329.v1
• Signetti, L., Elizarov, N., Simsir, M., Paquet, A., Douguet, D., Labbal, F., Debayle, D., Di Giorgio, A., Biou, V., Girard, C., et al. (2020). Inhibition of patched drug efflux increases vemurafenib effectiveness against resistant BrafV600E melanoma. Cancers 12 DOI 10.3390/cancers12061500

11:20

Claudine Mayer

Institut Pasteur, Paris

A new member of the type II topoisomerases, the meiotic topoisomerase-like complex

The SPO11 protein catalyzes the formation of meiotic DNA double strand breaks (DSBs) and is homologous to the A subunit of an archaeal topoisomerase (topo VI). Topo VI are heterotetrameric enzymes comprising two A and two B subunits. However, no topo VIB involved in meiotic recombination had been identified. We characterized a structural homolog of the archaeal topo VIB subunit [meiotic topoisomerase VIB–like (MTOPVIB)], which is essential for meiotic DSB formation. We showed that it forms a complex with the two Arabidopsis thaliana SPO11 orthologs required for meiotic DSB formation (SPO11-1 and SPO11-2) and is absolutely required for the formation of the SPO11-1/SPO11-2 heterodimer. We will present these findings that suggest that the catalytic core complex responsible for meiotic DSB formation in eukaryotes adopts a topo VI–like structure.

Selected references

• A DNA topoisomerase VI-like complex initiates meiotic recombination. Vrielynck N, Chambon A, Vezon D, Pereira L, Chelysheva L, De Muyt A, Mézard C, Mayer C, Grelon M. Science 2016 351(6276):939-43
• Overall structures of Mycobacterium tuberculosis DNA gyrase reveal the role of a Corynebacteriales GyrB-specific insert in ATPase activity. Petrella S, Capton E, Raynal B, Giffard C, Thureau A, Bonneté F, Alzari PM, Aubry A, Mayer C. Structure 2019 27(4):579-589
• Expanding the type IIB DNA topoisomerase family: identification of new topoisomerase and topoisomerase-like proteins in mobile genetic elements. T. Takahashi, V. Da Cunha, M. Krupovic, C. Mayer, P. Forterre, and D. Gadelle. NAR Genom Bioinform 2020, 2(1): lqz021
• Circular code motifs in the ribosome: a missing link in the evolution of translation? Dila G, Ripp R, Mayer C, Poch O, Michel CJ, Thompson JD. RNA 2019 25(12):1714-1730