Investigation of the activity and modes of action of VF16QKNS, an analog of thanatin, against gram-negative bacteria

• Main Author: Chong, Carina Wei Ting
• Other Authors: Surajit Bhattacharyya
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2023
• Subjects: Science::Biological sciences
• Online Access: https://hdl.handle.net/10356/169750
• Institution: Nanyang Technological University

The rapid emergence of antimicrobial resistance highlights the necessary development of novel antimicrobial compounds. Thanatin, a 21-residue long antimicrobial peptide, exhibits a broad spectrum of antimicrobial activity. In gram-negative bacteria, native thanatin’s dual mode of action comprises outer membrane (OM) permeabilization and periplasmic proteins binding which disrupt lipopolysaccharide (LPS) transport to the OM. This study aims to investigate the modes of action of thanatin analog VF16QKNS. Through MIC and checkerboard assays, OM permeabilization assays, interaction studies and NMR, this study has examined antibacterial activity, antibiotic potentiation abilities, LPS binding and the free structure of VF16QKNS. VF16QKNS exhibited potency against gram-negative strains and demonstrated OM permeabilizing, surface charge reducing and antibiotic potentiating capabilities. Greater OM permeabilization and surface charge reduction were observed for Escherichia coli relative to Pseudomonas aeruginosa. Antibiotic potentiation effects varied among antibiotics vancomycin, novobiocin and rifampicin, in Acinetobacter baumanni. ITC studies showed strong VF16QKNS-LPS binding of highly exothermic nature. Furthermore, NMR studies highlighted the importance of the β-hairpin structure for antibacterial activity. Overall, this study provides new insights for the design of future thanatin-based antimicrobial peptides.