Establishing the Structure-Activity Relationship between Phosphatidylglycerol and Daptomycin

Area of Science:

• Microbiology
• Biochemistry
• Medicinal Chemistry

Background:

• Daptomycin is a crucial antibiotic for Gram-positive bacterial infections.
• Its mechanism of action requires calcium and phosphatidylglycerol (PG), but the daptomycin-PG interaction is poorly understood.

Purpose of the Study:

• To elucidate the structure-activity relationship between daptomycin and phosphatidylglycerol (PG).
• To characterize the daptomycin-PG complex and its binding requirements.

Main Methods:

• Synthesis of nine phosphatidylglycerol (PG) analogs using phosphoramidite chemistry.
• Investigation of daptomycin-PG interactions using fluorescence, circular dichroism, and isothermal titration calorimetry.

Main Results:

• Daptomycin's binding is sensitive to PG headgroup modifications, with both hydroxyl groups being critical.
• A minimum PG acyl tail length of 7-8 carbons is necessary for micromolar binding.
• Daptomycin binds C8PGs similarly to PG in liposomes, indicating preassembly is not required.

Conclusions:

• The PG headgroup and acyl chain length are key determinants of daptomycin binding and activity.
• Daptomycin's interaction with PG is specific, involving a binding pocket that accommodates the PG headgroup's hydroxyls.
• Findings provide insights into daptomycin's mechanism of action and potential for drug development.