Glutamine Synthetase Drugability beyond Its Active Site: Exploring Oligomerization Interfaces and Pockets

Area of Science:

• Biochemistry
• Enzymology
• Drug Discovery

Background:

• Glutamine synthetase (GS) is vital for the nitrogen cycle and has commercial/pharmaceutical importance.
• Existing GS inhibitors lack specificity, affecting all organisms by targeting the active site.
• The protein-protein interface (PPI) of GS presents a novel target for developing selective enzyme inhibitors.

Purpose of the Study:

• To map the PPI of human (hsGS), maize (zmGS), and Mycobacterium tuberculosis (mtGS).
• To identify novel drugable pockets on GS PPIs for targeted inhibition.
• To explore the potential for developing organism-specific GS inhibitors.

Main Methods:

• Computational alanine scan mutagenesis was used to map PPI binding free energy.
• A multiple dielectric constant MM-PBSA methodology identified key residues (hot-spots).
• Fpocket software was employed to detect drugable pockets on GS.

Main Results:

• Identified 23, 19, and 30 hot-spots on hsGS, zmGS, and mtGS PPIs, respectively.
• hsGS and zmGS PPIs showed significant similarity, while mtGS PPI differed considerably.
• A novel drugable pocket was discovered on the mtGS PPI.

Conclusions:

• The mtGS PPI pocket is a promising target for selective anti-tuberculosis drug development.
• This pocket is distinct from hsGS and zmGS PPIs, suggesting targeted inactivity against eukaryotic GS II enzymes.
• Targeting this unique mtGS PPI pocket could lead to novel therapeutics with reduced off-target effects.