Total Synthesis and Preliminary Antibacterial Evaluation of the RNA Polymerase Inhibitors (±)-Myxopyronin A and B

Hu, Tao; Schaus, Jennifer V.; Lam, Kelvin; Palfreyman, Michael G.; Wuonola, Mark A.; Gustafson, Gary L.; Panek, James S.

doi:10.1021/jo9721610

Cited by 39 publications

(37 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Results are presented in Table 1. The results indicate, consistent with previous reports (19,20,31,33,49), that Myx exhibits potent antibacterial activity against both methicillin-sensitive S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) (MICs of 0.78 to 1.56 g/ ml). Results of spiral gradient endpoint MIC assays are identical, within one 2-fold serial dilution interval, to results of broth microdilution MIC assays.…”

Section: Resultssupporting

confidence: 81%

“…(Ϯ)-Myx B was synthesized as described in Hu et al (19). Rif was purchased from Sigma, Inc. Bacterial strains were obtained from the American Type Culture Collection.…”

Section: Methodsmentioning

confidence: 99%

“…The binding site on RNAP for Myx is different from the binding site on RNAP for the RNAP inhibitor in current use in broad-spectrum antibacterial therapy, rifampin (Rif) (3,18,32,49). Accordingly, Myx exhibits no cross-resistance with Rif (18,19,32,33,49).Previous studies have provided information about spontaneous resistance frequencies and resistance spectra for Myx (31, 32). However, the fitness costs of resistance have not previously been assessed.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Frequency, Spectrum, and Nonzero Fitness Costs of Resistance to Myxopyronin in Staphylococcus aureus

Srivastava

Degen

Ebright

2012

Antimicrob Agents Chemother

View full text Add to dashboard Cite

The antibiotic myxopyronin (Myx) functions by inhibiting bacterial RNA polymerase (RNAP). The binding site on RNAP for Myx-the RNAP "switch region SW1/SW2 subregion"-is different from the binding site on RNAP for the RNAP inhibitor currently used in broad-spectrum antibacterial therapy, rifampin (Rif). Here, we report the frequency, spectrum, and fitness costs of Myx resistance in Staphylococcus aureus. The resistance rate for Myx is 4 ؋ 10 ؊8 to 7 ؋ 10 ؊8 per generation, which is equal within error to the resistance rate for Rif (3 ؋ 10 ؊8 to 10 ؋ 10 ؊8 per generation). Substitutions conferring Myx resistance were obtained in the RNAP ␤ subunit [six substitutions: V1080(1275)I, V1080(1275)L, E1084(1279)K, D1101(1296)E, S1127(1322)L, and S1127 (1322) Mf50 (18,20,23,49). Myx exhibits broad-spectrum antibacterial activity, with potent antibacterial activity against most Gram-positive species and some Gram-negative species. Myx is under investigation as a potential lead compound for broad-spectrum antibacterial therapy. M yxopyronin (Myx) is an ␣-pyrone antibiotic produced by Myxococcus fulvusMyx functions by inhibiting bacterial RNA polymerase (RNAP) (3,18,20,32,49). The binding site on RNAP for Myx is located in the RNAP "switch region" and comprises the RNAP switch region structural elements termed "switch 1" and "switch 2," (switch region SW1/SW2 subregion) (3,18,32,49). The binding site on RNAP for Myx is different from the binding site on RNAP for the RNAP inhibitor in current use in broad-spectrum antibacterial therapy, rifampin (Rif) (3,18,32,49). Accordingly, Myx exhibits no cross-resistance with Rif (18,19,32,33,49).Previous studies have provided information about spontaneous resistance frequencies and resistance spectra for Myx (31, 32). However, the fitness costs of resistance have not previously been assessed.In this work, we comprehensively evaluate the resistance properties of Myx in Staphylococcus aureus. We report (i) the spontaneous resistance rate for Myx in S. aureus, (ii) the spontaneous resistance spectrum of Myx in S. aureus, and (iii) the fitness costs of substitutions that confer Myx resistance. Hu et al. (19). Rif was purchased from Sigma, Inc. Bacterial strains were obtained from the American Type Culture Collection. MATERIALS AND METHODS Materials. (Ϯ)-Myx B was synthesized as described inMICs. Minimal inhibitory concentrations (MICs) in column 2 of Table 1 were quantified using broth microdilution assays (8). MICs in column 3 of Table 1, and in Tables 3 and 4, were quantified using spiral gradient endpoint assays, essentially as described previously (38,45,54). Spiral gradient endpoint assays employed 150-mm by 4-mm exponentialgradient plates containing Mueller-Hinton II cation-adjusted agar and 0.5 to 100 g/ml of Myx, 0.0008 to 0.2 g/ml of Rif, or 0.2 to 40 g/ml of Rif. Plates were prepared using an Autoplate 4000 spiral plater (Spiral Biotech, Inc.). Cells were grown to early log phase, adjusted to 1 ϫ 10 8 CFU/ml, and swabbed radially onto plates. Plates were incubated for 16 h at 3...

show abstract

Section: Resultssupporting

confidence: 81%

“…(Ϯ)-Myx B was synthesized as described in Hu et al (19). Rif was purchased from Sigma, Inc. Bacterial strains were obtained from the American Type Culture Collection.…”

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Frequency, Spectrum, and Nonzero Fitness Costs of Resistance to Myxopyronin in Staphylococcus aureus

Srivastava

Degen

Ebright

2012

Antimicrob Agents Chemother

View full text Add to dashboard Cite

show abstract

“…Myx potently inhibits both Gram-positive bacterial RNAP and Gram-negative bacterial RNAP (IC50s in the low nanomolar range; Table 1; [11,12,24,27]) but does not inhibit eukaryotic RNAP [24]. Myx exhibits potent antibacterial activity against drug-sensitive and drug-resistant strains of a broad spectrum of Gram-positive bacteria, including Staphylococcus aureus, Enterococcus faecalis, Enterococcus faecium, Streptococcus pneumoniae, Clostridium difficile, Mycobacterium tuberculosis , and Bacillus anthracis (MICs = 1–13 µg/ml; Table 2; [12,24,27,28]). Myx also exhibits potent antibacterial activity against some Gram-negative bacteria, including Haemophilus influenzae, Moraxella catarrhalis , and Francisella tularensis (MICs = 6.1–16 µg/ml; Table 2).…”

Section: Introductionmentioning

confidence: 99%

New target for inhibition of bacterial RNA polymerase: ‘switch region’

Srivastava

Talaue

Liu

et al. 2011

Current Opinion in Microbiology

161

177

View full text Add to dashboard Cite

A new drug target-- the "switch region"--has been identified within bacterial RNA polymerase (RNAP), the enzyme that mediates bacterial RNA synthesis. The new target serves as the binding site for compounds that inhibit bacterial RNA synthesis and kill bacteria. Since the new target is present in most bacterial species, compounds that bind to the new target are active against a broad spectrum of bacterial species. Since the new target is different from targets of other antibacterial agents, compounds that bind to the new target are not cross-resistant with other antibacterial agents. Four antibiotocs that function through the new target have been identified: myxopyronin, corallopyronin, ripostatin, and lipiarmycin. This review summarizes the switch region, switch-region inhibitors, and implications for antibacterial drug discovery.

show abstract

“…The α-pyrone 36 and the holothin derivative 38 showed weak activities, whereas 37 produced no zone of inhibition. The synthesized (±)-myxopyronin B 15 was also tested; however, (±)-2 produced only a slight zone of inhibition in our assay system. Therefore, the authentic rifampicin (RFP) was used as a standard antibiotic in all assays.…”

mentioning

confidence: 99%

Novel Hybrid-Type Antimicrobial Agents Targeting the Switch Region of Bacterial RNA Polymerase

Yakushiji

Miyamoto

Kunoh

et al. 2013

ACS Med. Chem. Lett.

View full text Add to dashboard Cite

The bacterial RNA polymerase (RNAP) is an ideal target for the development of antimicrobial agents against drug-resistant bacteria. Especially, the switch region within RNAP has been considered as an attractive binding site for drug discovery. Here, we designed and synthesized a series of novel hybrid-type inhibitors of bacterial RNAP. The antimicrobial activities were evaluated using a paper disk diffusion assay, and selected derivatives were tested to determine their MIC values. The hybrid-type antimicrobial agent 29 showed inhibitory activity against Escherichia coli RNAP. The molecular docking study suggested that the RNAP switch region would be the binding site of 29. KEYWORDS: bacterial RNA polymerase, switch region, antimicrobial agent, bacterial RNA polymerase inhibitor, hybrid R ifamycins are a class of bacterial RNA polymerase (RNAP) inhibitors commonly used in clinical practice. The potency and broad-spectrum nature of rifamycins have improved the treatment of infectious diseases, including tuberculosis. Nevertheless, the emergence of drug-resistant bacteria poses an ongoing threat to the therapeutic index of rifamycins. For this reason, the development of a novel RNAP inhibitor is in demand. In 2008, a research team led by Arnold and Ebright elucidated the inhibitory mechanism of myxopyronin A (1) (Figure 1), 1 which was targeting the switch region of bacterial RNAP, and an X-ray crystal structure of 1 in complex with T. thermophilus RNAP was reported. 2,3 Corallopyronin (3) and ripostatins also appeared to bind to the RNAP switch region.2 Hence, this newly identified binding site in RNAP has attracted the attention of medicinal chemists to develop new antimicrobial agents. Before now, the research group of Simonsen and Xiang attempted a direct structure−activity relationship study of myxopyronin. 4,5 In addition, Fishwick and co-workers tried structure-based ligand design at the myxopyronin binding site. 6 On the other hand, Moy and co-workers reported that myxopyronin was an unsuitable lead compound for medicinal development because of the high binding to serum albumin, the low stability, and the occurrence of resistant strains. 7In this report, we disclose our effort to develop novel antimicrobial agents with a hybrid strategy 8,9 for myxopyronin derivatives. To enhance the antimicrobial activity, reduce the lipophilicity, and improve the instability, the antibiotic holomycin (4) 10 was incorporated into the mother skeleton of the myxopyronin-type RNAP inhibitors.Holomycin (4) also possessed antibacterial properties and provided moderate but broad antibiotic spectrum against 12 In addition, 4 showed the inhibition of RNA synthesis, 11 and the calculate log P (ClogP) did not exceed 2.0.13 These properties fascinated us to hybridize myxopyronins with the holothin molecule to expect the efficacy beyond our anticipations.Our hybrid strategy is shown in Figure 2. We designed two types of hybrid derivatives based on the reported X-ray crystal structure of RNAP with 1 (PDB: 3DXJ).2,3 One was th...

show abstract

Total Synthesis and Preliminary Antibacterial Evaluation of the RNA Polymerase Inhibitors (±)-Myxopyronin A and B

Cited by 39 publications

References 11 publications

Frequency, Spectrum, and Nonzero Fitness Costs of Resistance to Myxopyronin in Staphylococcus aureus

Frequency, Spectrum, and Nonzero Fitness Costs of Resistance to Myxopyronin in Staphylococcus aureus

New target for inhibition of bacterial RNA polymerase: ‘switch region’

Novel Hybrid-Type Antimicrobial Agents Targeting the Switch Region of Bacterial RNA Polymerase

Contact Info

Product

Resources

About