Hybrid Screening Approach for Very Small Fragments: X-ray and Computational Screening on FKBP51.

Area of Science:

• Structural Biology
• Computational Chemistry
• Drug Discovery

Background:

• Fragment-based drug discovery (FBDD) efficiently explores chemical space for identifying drug leads.
• X-ray crystallography and computational methods are crucial for determining fragment-protein interactions and guiding drug design.

Purpose of the Study:

• To map potential interaction sites on the FKBP51 FK1 domain using very small fragments (VSFs).
• To evaluate a hybrid screening strategy combining computational and experimental techniques for hit identification.

Main Methods:

• Screening of 15 VSFs (HA ≤ 11) using Site Identification by Ligand Competitive Saturation (SILCS) and X-ray crystallography.
• Determination of fragment:protein co-structures via X-ray crystallography.
• Affinity determination using 15N HSQC NMR.

Main Results:

• Identification of three hot spots on the FKBP51 FK1 domain.
• Obtained 6 X-ray co-structures, achieving a 40% hit rate.
• SILCS FragMaps showed overlap with X-ray structures, and identified similar interactions as known FK1 binders with millimolar affinities.

Conclusions:

• The hybrid SILCS and X-ray crystallography approach effectively identifies fragment hits and their binding poses.
• VSFs provide new chemical starting points for FKBP51 inhibitor development.
• Proposed hybrid screening strategy enables rapid identification of hits and binding poses.