Fig. 4

Electrostatic surface potential of Notch-1 ankyrin domain reflects the enrichment of acidic residues. a The electrostatic surface potential values for Notch-1 ankyrin (PDB: 1YYH), Swi6 (PDB: 1SW6), and NF-κB (PDB: 1IKN), calculated using Adaptive Poisson-Boltzmann Solver (APBS), are here reported. Surface potentials are on a [− 5,5] blue-white-green colour scale (kJ.mol⁻¹.e⁻¹). The top and the bottom panels provide a surface view of the β-hairpins and α-helices of the studied molecules, respectively. b The key acidic residues that populate the negatively charged pocket of the β-hairpins are highlighted in stick mode and labelled accordingly. The right cartoon shows a simplified view of the β-hairpins (βhp1-6) of human Notch-1 with acidic and basic residues highlighted in red and turquoise, respectively. Arrows point to two major evolutionary adaptations in β-hairpins of Notch-1 ankyrin domain, I. Substitution of ASN-1989 by ASP-1989 (refer to ANK4 of D. melanogaster as per Fig. 3b), and II. a reversal of the spatial order of ASP-ASN in ANK5 and ANK6 that enhances the anisotropic charge distribution