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Investigating the conformational dynamics of Zika virus NS4B protein

Zika virus (ZIKV) NS4B protein is a membranotropic protein having multifunctional roles such as evasion of host-immune system, and induction of host membrane rearrangement for viral genome replication and processing of polyprotein. Despite its versatile functioning, its topology and dynamics are not entirely understood. Presently, there is no NMR or X-ray crystallography-based structure available for any flaviviral NS4B protein. Therefore, in this study, we have investigated the structural dynamics of Zika Virus NS4B protein through 3D structure models using molecular dynamics (MD) simulations approach and experiments. Subsequently, we employed a reductionist approach to understand the dynamics of ZIKV NS4B protein. For this, we studied its N-terminal (residues 1-38), C-terminal (residues 194-251), and cytosolic (residues 131-169) regions in isolation. Further, we have performed experiments to prove the maximum dynamics in its cytosolic region. Using a combination of computational tools and circular dichroism (CD) spectroscopy, we validate the cytosolic region as an intrinsically disordered protein region (IDR). The microsecond-long all atoms molecular dynamics and replica-exchange MD simulations complement the experimental observations. We have also analysed its behaviour under the influence of differently charged liposomes and macromolecular crowding agents which may have significance on its overall dynamics. Lastly, we have proposed a ZIKV NS4B protein model illustrating its putative topology consisting of various membrane-spanning and non-membranous regions. Highlights Microsecond simulations of NS4B N-terminus and cytosolic regions exposed their dynamic nature. C-terminal region remains intact in presence lipid bilayer during 1 μs simulations. Spectroscopic results also reveal the cytosolic region as an intrinsically disordered region. Cytosolic region exhibits gain-of-structure property under helix inducing solvents.