Investigating protein-ligand interactions with a mutant FKBP possessing a designed specificity pocket

Area of Science:

• Biochemistry
• Structural Biology
• Drug Discovery

Background:

• FKBP12 is a protein target with a well-characterized ligand binding site.
• Structure-based drug design aims to create selective ligands by modifying protein binding pockets.
• Understanding ligand-protein interactions is crucial for developing targeted therapeutics.

Purpose of the Study:

• To remodel the FKBP12 ligand binding site to incorporate a hydrophobic specificity pocket.
• To investigate the binding characteristics and promiscuity of the engineered F36V-FKBP mutant.
• To analyze the structural basis of ligand binding and its impact on structure-activity relationships.

Main Methods:

• Structure-based design and protein mutagenesis were employed to create the F36V-FKBP mutant.
• Binding affinity assays were performed using novel synthetic ligands.
• Structural analysis of ligand-protein complexes, including X-ray crystallography or NMR spectroscopy, was utilized.
• Analysis of 'bumped' compounds provided insights into pocket promiscuity.

Main Results:

• The F36V-FKBP mutant successfully incorporated a sizable hydrophobic pocket.
• The mutant exhibited low or subnanomolar binding affinities for novel synthetic ligands.
• The engineered pocket demonstrated high promiscuity, accommodating diverse hydrophobic alkyl and aryl moieties.
• Ligand affinity was largely insensitive to pocket occupancy or packing quality.
• NMR analysis revealed that similar ligands could adopt different binding modes.

Conclusions:

• Remodeling the FKBP12 binding site created a promiscuous hydrophobic pocket.
• The promiscuity challenges traditional structure-activity relationship interpretations in drug design.
• This work highlights the complexity of designing highly specific binders even with engineered pockets.