Targeting Bacillus anthracis toxicity with a genetically selected inhibitor of the PA/CMG2 protein-protein interaction

• Published in: Scientific reports 2017-06, Vol.7 (1), p.3104-9, Article 3104
• Main Authors: Male, Abigail L., Forafonov, Fedor, Cuda, Francesco, Zhang, Gong, Zheng, Siqi, Oyston, Petra C. F., Chen, Peng R., Williamson, E. Diane, Tavassoli, Ali
• Format: Article
• Language: English
• Subjects: 140/131; 631/154/309/2419; 631/154/556; 631/1647/2163; 639/638/92/611; 82; Animals; Anthrax; Anti-Bacterial Agents - pharmacology; Antigens, Bacterial - metabolism; Bacillus anthracis; Bacillus anthracis - drug effects; Bacillus anthracis - physiology; Bacterial Toxins - metabolism; Binding sites; Cell Line, Tumor; Codons; Drug Discovery - methods; Edema; High-throughput screening; Humanities and Social Sciences; Lethal factor; Macrophages; multidisciplinary; Peptides; Phenylalanine; Protective antigen; Protein Binding - drug effects; Protein interaction; Proteins; Receptors, Peptide - metabolism; Science; Science (multidisciplinary); Toxicity; Toxins
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-017-03253-3

The protein-protein interaction between the human CMG2 receptor and the Bacillus anthracis protective antigen (PA) is essential for the transport of anthrax lethal and edema toxins into human cells. We used a genetically encoded high throughput screening platform to screen a SICLOPPS library of 3.2 million cyclic hexapeptides for inhibitors of this protein-protein interaction. Unusually, the top 3 hits all contained stop codons in the randomized region of the library, resulting in linear rather than cyclic peptides. These peptides disrupted the targeted interaction in vitro ; two act by binding to CMG2 while one binds PA. The efficacy of the most potent CMG2-binding inhibitor was improved through the incorporation of non-natural phenylalanine analogues. Cell based assays demonstrated that the optimized inhibitor protects macrophages from the toxicity of lethal factor.