Structure-Based Discovery of Lipoteichoic Acid Synthase Inhibitors

Area of Science:

• Biochemistry and Molecular Biology
• Antimicrobial Drug Discovery
• Structural Biology

Background:

• Lipoteichoic acid synthase (LtaS) is essential for Gram-positive bacterial cell wall integrity.
• LTA-deficient bacteria display impaired growth and cell division, highlighting LtaS as a potential antimicrobial target.
• Limited small-molecule inhibitors and lack of structural data hinder structure-based drug discovery for LtaS.

Purpose of the Study:

• To model the binding of a known inhibitor (compound 1771) to LtaS using computational methods.
• To optimize compound 1771 into a more potent inhibitor (compound 4).
• To explore novel inhibitor classes by screening against a computationally identified cryptic pocket in LtaS.

Main Methods:

• Molecular docking and molecular dynamics (MD) simulations to predict compound 1771 binding.
• Alanine mutagenesis and isothermal titration calorimetry for model validation.
• Lead optimization, in vitro assays, bacterial morphology analysis, and in vivo infection models.
• Virtual screening (VS) targeting a transient cryptic pocket identified via MD simulations.

Main Results:

• A validated model of compound 1771 bound to the extracellular domain of LtaS (eLtaS) was generated.
• Compound 4, an optimized analog, demonstrated enhanced binding affinity and potent inhibition of LTA production in *S. aureus*.
• Compound 4 reduced bacterial load in a murine lung infection model and induced aberrant bacterial morphology.
• Virtual screening identified a new class of LtaS inhibitors, potentiating β-lactams against MRSA.

Conclusions:

• The study presents a successful structure-based drug design workflow for LtaS, yielding a potent inhibitor and novel drug leads.
• The findings validate the importance of considering protein conformational flexibility in virtual screening.
• This work provides a foundation for developing new antimicrobial agents targeting LtaS.