The NCBI structure viewer iCn3D version 3 is now available on the NCBI web site and from GitHub.
Analysis of 3D Structures
You can use the current version with the icn3d package at npm to write scripts to call functions in iCn3D. For example, this script on GitHub can calculate the change in interactions due to a mutation. The results of this analysis for the structure (6M0J) of the SARS-CoV-2 spike protein bound to the ACE2 receptor are displayed in Figure 1. These show the predicted changes in interactions with other residues in the the SARS-CoV-2 spike protein and in the ACE2 receptor when the asparagine (N) at position 501 of the spike protein is changed to a tyrosine (Y). You can also run these scripts from the command line to process a list of 3D structures to get and analyze annotations.
Figure 1. iCn3D viewer showing the predicted interactions with other residues in the spike protein and in the ACE2 target when the asparagine (N) at position 501 of the SARS-CoV-2 spike protein is substituted with tyrosine (Y), highlighted in yellow. Interactions were calculated using the script interactions2.js.
The NCBI structure viewer iCn3D 2.20.0 is now available on the NCBI web site and from GitHub. You can now view the electrostatic potential map for any subset of 3D structures within 30,000 atoms. The potential is calculated using the DelPhi program by solving a linear Poisson-Boltzmann equation. You can show the potential on a surface or show a equipotential map. The potential map shows the effect of charges on molecular interactions qualitatively.
The example in Figure 1 below shows the electrostatic potential for the binding of Gleevec to the human Abl2 protein. This new feature can be accessed from the menu “Analysis > DelPhi Potential.” You can also download the PQR file format with assigned partial charges.
Figure 1: 3GVU: The crystal structure of human ABL2 in complex with GLEEVEC. The ligand shows the -25 mV (red) and +25 mV (blue) equipotential map with a grid size 65, salt concentration 0.15 M, and pH 7. The protein shows the surface potential with a gradient from -75 mV (red) to +75 mV (blue).
A recent article by Wang J., et al. describes the features and applications of iCn3D, NCBI’s web-based 3D viewer (Figure 1), and shows how you can use it for interactive structural analysis.
Wang J, Youkharibache P, Zhang D, Lanczycki CJ, Geer RC, Madej T, Phan L, Ward M, Lu S, Marchler GH, Wang Y, Bryant SH, Geer LY, Marchler-Bauer A. iCn3D, a Web-based 3D Viewer for Sharing 1D/2D/3D Representations of Biomolecular Structures. Bioinformatics. 2019 June 20; pii: btz502. doi: 10.1093/bioinformatics/btz502. (PMID: 31218344)