Potato virus Y (PVY) belongs to the most economically important pathogens. The collaborative research project of the National Institute of Chemistry (Ljublana, Slovenia) and Cryo-Electron Microscopy Core Facility at CEITEC MU reveals the structure of the PVY coat protein (CP) and the PVY virus like particle at near-atomic resolution. The data show a novel luminal interplay between the extended carboxy-terminal CP regions in the virion and describe RNA-CP interactions important for helical conformation and stability of the virus.

Marjetka Podobnik Research Group

Significance

PVY is ranked as fifth in the top 10 most economically important plant viruses and is the most important viral pathogen of potato worldwide. The virus causes potato tuber necrotic ringspot disease, which can result in up to 70% yield reduction, and severely affects other economically important solanaceous crops. Despite extensive availability of data on PVY’s genome and pathogenicity, there has been no high-resolution structuralinformation for this virus. Because of the extreme economic importance of PVY, and the urgent need for structural data to better understand mechanisms of viral infectivity, we have examined in detail the structure of the PVY virion and its CP. We have determined the high-resolution electron cryo-microscopy structures of the PVY virion and a recombinant PVY-based RNA-free virus-like particle (VLP). This provides a new and detailed insight into the RNA-supported helical viral capsid architecture featuring an extended C-terminal region of CP, which is tightly packed in a unique fashion in the virion lumen. In addition, using extensive biochemical, biophysical, and computational characterization, as well as structure-­based mutagenesis, we identified regions of CP that affect VLP filament assembly. Moreover, the biological activities of the CP’s N- and C-terminal regions for virus infectivity were explored by measuring the accumulation of viral RNA and systemic movement of selected PVY mutants in plants.

Kežar, A., Kavčič, L.,  Polák, M., Nováček, J., Gutiérrez-Aguirre, I., Tušek Žnidarič, M., Coll, A., Stare, K., Gruden, K., Ravnikar, M., Pahovnik, D., Žagar, E., Merzel, F., Anderluh,G., and Podobnik, M.: Structural basis for the multitasking nature of the potato virus Y coat protein, Sci. Adv. (2019) 5(7), eaaw3808, DOI: 10.1126/sciadv.aaw3808

In biology, the transport of ions across lipid membranes is crucial and is generally performed by membrane proteins. Deficiencies in transport are at the origin of various diseases, such as cystic fibrosis. In this context, synthetic anion carriers incorporated within the lipid bilayer could play a remedial role. They extract ions from one side of the membrane, move across, and release the ions on the other side.

Vladimír Šindelář Research Group

Significance

The exchange of chloride and bicarbonate across lipid bilayers is an important biological process. Synthetic molecules can act as mobile carriers for these anions, although most show little selectivity. Here we report on three bambus[6]uril macrocycles functionalized with fluorinated benzyl groups, which are ableto exchange Cl^-and HCO₃^-efficiently. Remarkably, rates for Cl^-/NO₃^- exchangeare two orders of magnitude lower. The higher rates of Cl^-/HCO₃^-transport can be explained by the ability of the bambusurils to complex Cl^- and HCO₃^-simultaneously, facilitating their exchange at the bilayer interface.

Furthermore, the exceptionally high affinity and selectivity of these systemsfor NO₃^-appear to contribute to the poor Cl^-/NO₃^-exchange. This worknot only demonstrates the importance of anion binding characteristics onanion transport but also the potential relevance of bambusurils for aniontransport applications considering the high rate observed for Cl^-/HCO₃^-exchange.

Valkenier, H., Akrawi, O., Jurcek, P., Sleziakova, K., Lizal, T., Bartik, K. and Sindelar, V.: Fluorinated Bambusurils as Highly Effective and Selective Transmembrane Cl^-/HCO₃^-Antiporters, Chem(2019) 5, 429-444. doi:10.1016/j.chempr.2018.11.008