Unlike dengue virus, the conserved 14-23 residues in N-terminal region of Zika virus capsid is not involved in lipid interactions

Zika virus capsid protein is involved in multiple essential steps of the viral life cycle. Many vital functionalities are attributed to the dynamic N- terminal domain of this protein, which is intrinsically disordered in ZIKV and among several flaviviruses too. Other than genome encapsulation, studies have shown interaction with host lipid droplets to be crucial for replication and maturation. In Dengue virus, the molecular basis of such interplay has been studied in detail, and residues within the capsid N-terminal disordered domain has been mapped. It revealed a new function of a conserved region in mediating capsid-lipid droplet association through a conformational transition. Therefore, in this study, we attempt to analyze the structural dynamics of Zika virus capsid's N- terminal domain and analyzed it through a reductionist approach by dividing the N-terminal domain into three truncated segments and studied them individually. Techniques such as Circular dichroism spectroscopy, Dynamic light scattering, Zeta potential and Molecular dynamic simulations were employed to identify the motif responsible for structural flexibility and ability to interact with membrane models. Our results confirm that the truncated segments 5-26 and 1-30 readily adopt an a-helical conformation in the presence of 2,2,2-trifluoro-ethanol, detergent and negatively charged phospholipids. However, in contrast to Dengue virus, we report the conserved residues 14-23 region to be unstructured and do not undergo a conformational switch in Zika virus. Thus, our study illustrates the possibility of conserved 14-23 region's non-involvement in ZIKV capsid-lipid droplet association, unlike DENV.