Structure features of Streptococcus pneumoniae FabG and virtual screening of allosteric inhibitors

Area of Science:

• Structural Biology
• Drug Discovery
• Microbiology

Background:

• Streptococcus pneumoniae causes global infections, with rising antibiotic resistance posing a significant public health threat.
• The type II fatty acid synthase (FAS II) system, particularly the 3-oxoacyl-[acyl-carrier-protein] reductase (FabG) enzyme, is a promising target for novel antibacterial drug development.
• Understanding SpFabG's structure and function is crucial for designing effective inhibitors against S. pneumoniae.

Purpose of the Study:

• To elucidate the structure and function of Streptococcus pneumoniae 3-oxoacyl-[acyl-carrier-protein] reductase (SpFabG).
• To identify potential drug candidates that inhibit SpFabG activity.
• To investigate the structural basis of SpFabG's oligomerization and its implications for enzyme activity.

Main Methods:

• X-ray diffraction was used to determine the 2 Å structure of SpFabG.
• In vitro and in vivo functional assays were performed to characterize SpFabG.
• Mutagenesis studies were conducted to investigate the role of the tetramerization site.
• A large-scale virtual screening workflow, including pharmacophore-based screening, molecular docking, and binding energy calculations, was employed.

Main Results:

• The NADPH binding to SpFabG induced a conformational change from tetramers to dimers, suggesting dimers as the active form.
• A conserved tetramerization site was identified, and mutations within this site led to loss of function and destabilization.
• Virtual screening of over 500,000 compounds identified L1, L2, and L5 as promising SpFabG inhibitors based on stable binding modes.

Conclusions:

• SpFabG is a validated target for anti-streptococcal drug development.
• The dimeric form of SpFabG is likely the active conformation, regulated by NADPH binding.
• L1, L2, and L5 represent promising lead compounds for further development into novel antibiotics against S. pneumoniae.