Nucleobindin-2 consists of two structural components: The Zn-sensitive N-terminal half, consisting of nesfatin-1 and -2, and the Ca-sensitive C-terminal half, consisting of nesfatin-3.

Nucleobindin-2 (Nucb2) is a protein that has been suggested to play roles in a variety of biological processes. Nucb2 contains two Ca/Mg-binding EF-hand domains separated by an acidic amino acid residue-rich region and a leucine zipper. All of these domains are located within the C-terminal half of the protein. At the N-terminal half, Nucb2 also possesses a putative Zn-binding motif. In our recent studies, we observed that Nucb2 underwent Ca-dependent compaction and formed a mosaic-like structure consisting of intertwined disordered and ordered regions at its C-terminal half. The aim of this study was to investigate the impact of two other potential ligands: Mg, which possesses chemical properties similar to those of Ca, and Zn, for which a putative binding motif was identified. In this study, we demonstrated that the binding of Mg led to oligomerization state changes with no significant secondary or tertiary structural alterations of Nucb2. In contrast, Zn binding had a more pronounced effect on the structure of Nucb2, leading to the local destabilization of its N-terminal half while also inducing changes within its C-terminal half. These structural rearrangements resulted in the oligomerization and/or aggregation of Nucb2 molecules. Taken together, the results of our previous and current research help to elucidate the structure of the Nucb2, which can be divided into two parts: the Zn-sensitive N-terminal half (consisting of nesfatin-1 and -2) and the Ca-sensitive C-terminal half (consisting of nesfatin-3). These results may also help to open a new discussion regarding the diverse roles that metal cations play in regulating the structure of Nucb2 and the various physiological functions of this protein.