Fluoroquinolone interactions with Mycobacterium tuberculosis gyrase: Enhancing drug activity against wild-type and resistant gyrase

Abstract

Mycobacterium tuberculosis is a significant source of global morbidity and mortality. Moxifloxacin and other fluoroquinolones are important therapeutic agents for the treatment of tuberculosis, particularly multidrug-resistant infections. To guide the development of new quinolone-based agents, it is critical to understand the basis of drug action against M. tuberculosis gyrase and how mutations in the enzyme cause resistance. Therefore, we characterized interactions of fluoroquinolones and related drugs with WT gyrase and enzymes carrying mutations at GyrA A90 and GyrA D94. M. tuberculosis gyrase lacks a conserved serine that anchors a water-metal ion bridge that is critical for quinolone interactions with other bacterial type II topoisomerases. Despite the fact that the serine is replaced by an alanine (i.e., GyrA A90 ) in M. tuberculosis gyrase, the bridge still forms and plays a functional role in mediating quinolone-gyrase interactions. Clinically relevant mutations at GyrA A90 and GyrA D94 cause quinolone resistance by disrupting the bridge-enzyme interaction, thereby decreasing drug affinity. Fluoroquinolone activity against WT and resistant enzymes is enhanced by the introduction of specific groups at the C7 and C8 positions. By dissecting fluoroquinolone-enzyme interactions, we determined that an 8-methyl-moxifloxacin derivative induces high levels of stable cleavage complexes with WT gyrase and two common resistant enzymes, GyrA A90V and GyrA D94G. 8-Methyl-moxifloxacin was more potent than moxifloxacin against WT M. tuberculosis gyrase and displayed higher activity against the mutant enzymes than moxifloxacin did against WT gyrase. This chemical biology approach to defining drug-enzyme interactions has the potential to identify novel drugs with improved activity against tuberculosis.Mycobacterium tuberculosis | fluoroquinolones | antibiotic resistance | gyrase | complex stability

Role of gyrB Mutations in Pre-extensively and Extensively Drug-Resistant Tuberculosis in Thai Clinical Isolates

“…In this study, we found a relatively high prevalence of mutations in QRDR-A, at 96.7% among isolates examined, and the most frequent mutations occurred in GyrA at D94 (72.7%). Because the D94 residue, which anchors the water-magnesium ion bridge with a conserved C3/C4 keto acid moiety of quinolones, plays an important role in stabilizing the quinolone molecule in the QBP, an amino acid substitution at this position will exaggerate the deleterious effect of the binding between most quinolones and DNA gyrase (41,42). In addition, the high frequency of D94 mutations in clinical isolates from pre-XDR and XDR-TB may be due to the positive epistasis between D94 mutations and mutations conferring rifampin resistance leading to the progression of MDR-TB to XDR-TB (43).…”

Crystal structure and stability of gyrase–fluoroquinolone cleaved complexes from Mycobacterium tuberculosis

“…1A) increases activity against mycobacteria, particularly resistant mutants (18)(19)(20). Indeed, moxifloxacin, along with a more active C8-methyl derivative, retains high inhibitory activity against purified Mtb gyrase even when the enzyme contains commonly acquired fluoroquinoloneresistance substitutions [as described in the accompanying paper by Aldred et al (21)]. In another example, quinazolinediones (diones) have been shown to have an ability to bypass existing resistance within mycobacteria and other bacterial species (20,(22)(23)(24).…”

“…One notable, watermediated magnesium-ion contact is with Asp94 of GyrA; this interaction likely accounts for why many substitutions at Asp94 lead to drug insensitivity in fluoroquinolone-resistant laboratory and clinical strain isolates (11,47) (see also ref. 21). …”

Thiophene antibacterials that allosterically stabilize DNA-cleavage complexes with DNA gyrase

“…Unfortunately, despite this dual targeting, the rise of clinical resistance to FQs, most commonly by mutation in the conserved GyrA S83 and D87 amino acid residues (Escherichia coli numbering), has compromised the use of this important class of antibiotics, especially in infections caused by Gram-positive and -negative pathogens (13) and in MDR tuberculosis (14).…”