Protein-ligand docking is a crucial component of molecular modeling and drug discovery workflows. Accurately predicting how a ligand binds to a protein can lead to life-changing discoveries, such as finding potential drug candidates or better understanding molecular mechanisms. However, the process can be intricate and time-consuming. Enter the FITTED Suite, a SAMSON Extension developed to streamline protein-ligand docking workflows.
One of the standout features of the FITTED Suite is its ability to handle both covalent and non-covalent protein-ligand docking. Whether you are exploring hydrogen bonding networks, metalloproteins, or structure-based drug design for kinases, the suite offers tools to simplify and automate complex processes. In this blog, we’ll walk you through the essential steps for non-covalent docking and show you how the FITTED Suite can empower your analyses.
Streamlined Setup for Non-Covalent Docking
The FITTED Suite in SAMSON makes preparing and running docking simulations an intuitive process. Let’s take an example of docking a thymidine kinase protein structure (1E2K) bound to the ligand (N)-methanocarba-thymidine (TMC 500). Follow these steps:
1. Open the Protein and Ligand File
Launch SAMSON and open the provided file 1E2K-A.sam. You can do this by dragging and dropping the file into SAMSON or selecting Home > Open. This will display the structural model of the protein and ligand within SAMSON’s Document view.
2. Define the Docking System
Once the file is loaded, open the FITTED Suite by navigating to Home > Apps > Biology. Here, you will set up the system by defining three critical components: the receptor (protein), the binding site, and the ligand.
- Receptor: Select the 1E2K structural model and use Set receptor > From document. Leave parameters like Water molecules as default.
- Binding Site: Specify the binding site based on the already bound ligand (TMC 500). Locate and select the ligand in the Document view, then click Set binding site > From bound ligand.
- Ligand: Similarly, select TMC 500 as the ligand from the Document view and click Set ligand > From document. Check the option to prepare the ligand (add hydrogens, adjust bond orders, etc.).
3. Launch the Docking Simulation
Before running, set docking parameters in the FITTED Suite:
- Set the number of runs to 2 (or an appropriate value for your study).
- Enable “Import only best pose” if desired.
- Set the docking mode to Non-covalent.
Click the Dock button to start the simulation. The calculation progress and logs will be displayed for user convenience.
4. Inspect the Results
Once the docking completes, the best ligand poses will automatically load into the document. The results will also populate a table in the FITTED Suite interface, offering options to export or analyze in further detail.
In SAMSON’s Document view, you’ll see a processed receptor model (1E2K_pro) with added hydrogens and the corresponding ligand pose. For convenience, you can hide the initial structure and visualize the results:
5. Visual Refinement and Analysis
To make visual analysis easier, SAMSON allows for advanced customization:
- Add ribbons or secondary structure visual models to the receptor for clarity.
- Highlight binding sites with licorice representations or colorize residues for better organization.
- Measure distances and explore precise ligand-receptor interactions.
For detailed insights, you can even integrate additional SAMSON tools, such as the Protein-Ligand Interaction Analyzer Extension.
The Advantage of the FITTED Suite
With its intuitive setup and integration into SAMSON’s unified environment, the FITTED Suite eliminates the common bottlenecks in protein-ligand docking. Instead of tedious manual adjustments, you get support for flexible macromolecular targets, water molecules, covalent interactions, and more—all with a few clicks.
If you’re curious about refining your workflows further, check out the original documentation page here.
Note: SAMSON and all SAMSON Extensions are free for non-commercial use. Get SAMSON at https://www.samson-connect.net.