Inhibiting mycobacterial tryptophan synthase by targeting the inter-subunit interface

Area of Science:

• Medicinal Chemistry
• Microbiology
• Structural Biology

Background:

• Drug discovery for Mycobacterium tuberculosis (Mtb) relies on phenotypic screens.
• Sulfolane and indoline-5-sulfonamide compounds emerged as potent inhibitors of mycobacterial growth.
• Further optimization yielded compound 4 with in vivo efficacy in a murine model.

Purpose of the Study:

• To identify the specific molecular target and inhibition mechanism of novel anti-tubercular compounds.
• To validate tryptophan synthase as a viable drug target against Mtb.

Main Methods:

• Whole genome sequencing of spontaneous resistant Mtb mutants to identify resistance-conferring mutations.
• Over-expression studies to confirm the biological target.
• Biochemical assays to probe the inhibition mechanism.
• Structural analysis of Mtb tryptophan synthase mutations.

Main Results:

• Mutations conferring resistance were located in the essential α- and β-subunits of tryptophan synthase.
• Tryptophan synthase was confirmed as the biological target.
• Mutant enzymes incurred a fitness cost but retained inhibitor binding capacity.
• Resistance mutations mapped to the α-β subunit interface of Mtb tryptophan synthase.

Conclusions:

• Novel anti-tubercular agents targeting tryptophan synthase have been discovered.
• Tryptophan synthase represents a promising therapeutic target for tuberculosis treatment.
• Amino acid biosynthetic pathways are potential future targets for Mtb drug development.