Structure, Function, and Inhibition of Staphylococcus aureus Heptaprenyl Diphosphate Synthase

Area of Science:

• Biochemistry
• Structural Biology
• Microbiology

Background:

• Heptaprenyl diphosphate synthase (HepPPS) is essential for menaquinone biosynthesis in bacteria.
• Menaquinone is a critical electron transporter in many bacterial pathogens, including Staphylococcus aureus.
• Inhibiting menaquinone production is a potential strategy for developing novel antibiotics.

Purpose of the Study:

• To determine the first structure of Staphylococcus aureus heptaprenyl diphosphate synthase (SaHepPPS).
• To investigate the enzyme's mechanism of action and identify potential inhibitors.
• To explore the development of menaquinone biosynthesis inhibitors as antibiotic leads.

Main Methods:

• X-ray crystallography was used to determine the structure of SaHepPPS.
• Enzyme kinetics were employed to study the mechanism of action and inhibition.
• In vitro assays were performed to evaluate the activity of identified inhibitors against S. aureus growth.

Main Results:

• The structure of SaHepPPS, comprising catalytic (SaHepPPS-2) and regulatory (SaHepPPS-1) subunits, was elucidated.
• High substrate concentrations and bisphosphonates were found to inhibit SaHepPPS.
• N-alkyl analogues of zoledronate with C6 alkyl chains exhibited potent inhibition (Ki ~200 nM) and modest activity against S. aureus cell growth, which was partially rescued by menaquinone-7.

Conclusions:

• The determined structure of SaHepPPS provides a basis for rational drug design.
• SaHepPPS is a validated target for developing inhibitors of menaquinone biosynthesis.
• Inhibitors of SaHepPPS represent promising leads for novel antibiotic development against Staphylococcus aureus infections.