Molecular Determinants Governing the Antitubercular Activity of Griselimycin

Area of Science:

• Microbiology
• Medicinal Chemistry
• Drug Discovery

Background:

• Tuberculosis (TB) remains a leading infectious cause of death, with over a million annual fatalities.
• Drug-resistant Mycobacterium tuberculosis (Mtb) strains necessitate urgent development of new anti-TB drugs.
• Griselimycin (GM) is a cyclic peptide antibiotic targeting the Mtb DNA sliding clamp, but its structure-activity relationship (SAR) is poorly understood.

Purpose of the Study:

• To comprehensively investigate the SAR of Griselimycin (GM).
• To identify essential amino acid residues for GM's antibiotic activity.
• To guide the rational design of novel GM analogues for improved anti-TB therapies.

Main Methods:

• An alanine scan library of GM was synthesized and tested for antibiotic activity against M. tuberculosis and M. smegmatis.
• The impact of N-methylation, cyclization chemistry, and unnatural amino acid incorporation was evaluated.
• A fluorophore-tagged GM analogue was used to visualize drug accumulation within mycobacteria and macrophages.

Main Results:

• Key amino acid residues essential for GM's activity and amenable to modification were identified.
• Backbone N-methylation and modifications to cyclization chemistry were assessed for their impact on activity.
• Visualization confirmed GM accumulation within mycobacteria, including intracellularly within macrophages.

Conclusions:

• This study provides the first comprehensive SAR analysis of Griselimycin.
• Identified modifications can inform the rational design of next-generation Griselimycin-based anti-tuberculosis agents.
• Understanding GM's SAR and cellular accumulation is crucial for developing effective TB treatments.