Molecular Dynamics Studies of the Nucleoprotein of Influenza A Virus: Role of the Protein Flexibility in RNA Binding

The influenza viruses contain a segmented, negative stranded RNA genome. Each RNA segment is covered by multiple copies of the nucleoprotein (NP). X-ray structures have shown that NP contains well-structured domains juxtaposed with regions of missing electron densities corresponding to loops. In this study, we tested if these flexible loops gated or promoted RNA binding and RNA-induced oligomerization of NP. We first performed molecular dynamics simulations of wt NP monomer and trimer in comparison with the R361A protein mutated in the RNA binding groove, using the H1N1 NP as the initial structure. Calculation of the root-mean-square fluctuations highlighted the presence of two flexible loops in NP trimer: loop 1 (73–90), loop 2 (200–214). In NP, loops 1 and 2 formed a 10–15 Å-wide pinch giving access to the RNA binding groove. Loop 1 was stabilized by interactions with K113 of the adjacent β-sheet 1 (91–112) that interacted with the RNA grove (linker 360–373) via multiple hydrophobic contacts. In R361A, a salt bridge formed between E80 of loop 1 and R208 of loop 2 driven by hydrophobic contacts between L79 and W207, due to a decreased flexibility of loop 2 and loop 1 unfolding. Thus, RNA could not access its binding groove in R361A; accordingly, R361A had a much lower affinity for RNA than NP. Disruption of the E80-R208 interaction in the triple mutant R361A-E80A-E81A increased its RNA binding affinity and restored its oligomerization back to wt levels in contrast with impaired levels of R361A. Our data suggest that the flexibility of loops 1 and 2 is required for RNA sampling and binding which likely involve conformational change(s) of the nucleoprotein

Convergent synthesis and properties of photoactivable NADPH mimics targeting nitric oxide synthases

International audienceA new series of photoactivable NADPH mimics bearing one or two O-carboxymethyl groups on the adenosine moiety have been readily synthesized using click chemistry. These compounds display interesting one- or two-photon absorption properties. Their fluorescence emission wavelength and quantum yields (Phi) are dependent on the solvent polarity, with a red-shift in a more polar environment (lambda(max,em) = 460-467 nm, Phi > 0.53 in DMSO, and lambda(max,em) = 475-491 nm, Phi < 0.17 in Tris). These compounds show good binding affinity towards the constitutive nNOS and eNOS, confirming for the first time that the carboxymethyl group can be used as a surrogate of phosphate. Two-photon fluorescence imaging of nanotriggers in living cells showed that the presence of one carboxymethyl group (especially on the 3' position of the ribose) strongly favors the addressing of nanotriggers to eNOS in the cell context

New forms of social security for persons moving between the EU and the UK

This topical and important book identifies the short to medium-term economic, financial and social consequences of Brexit. Containing perspectives from leading thinkers across legal, economic and financial fields, it considers both the general effect of UK withdrawal on the European integration process, and the specific impact on the free movement of capital, goods and people. Addressing the main areas within both the UK and the EU that can and will be affected by Brexit, including the financial sector, immigration, social rights and social security, After Brexit: Consequences for the European Union will make fascinating reading for all those currently engaged in the study and practice of Law, Economics, Finance, Political Science, Philosophy, History and International Affairs