Gyramides prevent bacterial growth by inhibiting DNA gyrase and altering chromosome topology.

Antibiotics targeting DNA gyrase have been a clinical success story for the past half-century, and the emergence of bacterial resistance has fueled the search for new gyrase inhibitors. In this paper we demonstrate that a new class of gyrase inhibitors, the gyramides, are bacteriostatic agents that competitively inhibit the ATPase activity of Escherichia coli gyrase and produce supercoiled DNA in vivo. E. coli cells treated with gyramide A have abnormally localized, condensed chromosomes that blocks DNA replication and interrupts chromosome segregation. The resulting alterations in DNA topology inhibit cell division through a mechanism that involves the SOS pathway. Importantly, gyramide A is a specific inhibitor of gyrase and does not inhibit the closely related E. coli enzyme topoisomerase IV. E. coli mutants with reduced susceptibility to gyramide A do not display cross-resistance to ciprofloxacin and novobiocin. The results demonstrate that the gyramides prevent bacterial growth by a mechanism in which the topological state of chromosomes is altered and halts DNA replication and segregation. The specificity and activity of the gyramides for inhibiting gyrase makes these compounds important chemical tools for studying the mechanism of gyrase and the connection between DNA topology and bacterial cell division.

N-Benzyl-3-sulfonamidopyrrolidines are a New Class of Bacterial DNA Gyrase Inhibitors.

This paper characterizes N-benzyl-3-sulfonamidopyrrolidines (gyramides) as DNA gyrase inhibitors. Gyramide A was previously shown to exhibit antimicrobial activity that suggested it inhibited bacterial cell division. In this study, we conducted target identification studies and identified DNA gyrase as the primary target of gyramide A. The gyramide A resistance-determining region in DNA gyrase is adjacent to the DNA cleavage gate and is a new site for inhibitor design. We studied the antibiotic effects of gyramides A-C in combination with the Gram-negative efflux pump inhibitor MC-207,110 (60 µM). The gyramides had a minimum inhibitory concentration of 10-40 µM against Escherichia coli, Pseudomonas aeruginosa, Salmonella enterica, Staphylococcus aureus, and Streptococcus pneumoniae; the compounds were ineffective against Enterococcus faecalis. The IC(50) of gyramides A-C against E. coli DNA gyrase was 0.7- 3.3 µM. The N-benzyl-3-sulfonamidopyrrolidines described in this manuscript represent a starting point for development of antibiotics that bind a new site in DNA gyrase.