Okada, A. et al. Walkmycin B targets WalK (YycG), a histidine kinase essential for bacterial cell growth. J. Antibiot. 63, 89-94

Department of Bioscience, Graduate School of Agriculture, Kinki University, Nara, Japan.
The Journal of Antibiotics (Impact Factor: 1.73). 02/2010; 63(2):89-94. DOI: 10.1038/ja.2009.128
Source: PubMed


The WalK (a histidine kinase)/WalR (a response regulator, aka YycG/YycF) two-component system is indispensable in the signal transduction pathway for the cell-wall metabolism of Bacillus subtilis and Staphylococcus aureus. The inhibitors directed against WalK would be expected to have a bactericidal effect. After we screened 1368 culture broths of Streptomyces sp. by a differential growth assay, walkmycin A, B and C, which were produced by strain MK632-100F11, were purified using silica-gel column chromatography and HPLC. In this paper, the chemical structure of the major product (walkmycin B) was determined to be di-anthracenone (C(44)H(44)Cl(2)O(14)), which was very similar to BE40665A. MICs of walkmycin B against B. subtilis and S. aureus were 0.39 and 0.20 microg ml(-1), and IC(50) measurements against WalK were 1.6 and 5.7 microM, respectively. To clarify the affinity between WalK and walkmycin B, surface plasmon resonance was measured to obtain the equilibrium dissociation constant, K(D1), of 7.63 microM at the higher affinity site of B. subtilis WalK. These results suggest that walkmycin B inhibits WalK autophosphorylation by binding to the WalK cytoplasmic domain.

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    • "Inhibitors against YycG or YycF are bactericidal for gram-positive pathogens (Okada et al. 2010). It has been reported that the inhibitors walkmycin B that targets YycG and walrycin A/B that targets YycF are effective against Bacillus subtilis and S. aureus at low MICs, though efficacy against biofilms has not been described (Okada et al. 2010; Watanabe et al. 2003). Fig. 4 Bactericidal effect of derivatives on mature biofilms of S. epidermidis observed by CLSM. "
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    ABSTRACT: Treating staphylococcal biofilm-associated infections is challenging. Based on the findings that compound 2 targeting the HK domain of Staphylococcus epidermidis YycG has bactericidal and antibiofilm activities against staphylococci, six newly synthesized derivatives were evaluated for their antibacterial activities. The six derivatives of compound 2 inhibited autophosphorylation of recombinant YycG′ and the IC50 values ranged from 24.2 to 71.2 μM. The derivatives displayed bactericidal activity against planktonic S. epidermidis or Staphylococcus aureus strains in the MIC range of 1.5–3.1 μM. All the derivatives had antibiofilm activities against the 6- and 24-h biofilms of S. epidermidis. Compared to the prototype compound 2, they had less cytotoxicity for Vero cells and less hemolytic activity for human erythrocytes. The derivatives showed antibacterial activities against clinical methicillin-resistant staphylococcal isolates. The structural modification of YycG inhibitors will assist the discovery of novel agents to eliminate biofilm infections and multidrug-resistant staphylococcal infections. Electronic supplementary material The online version of this article (doi:10.1007/s00253-014-5685-8) contains supplementary material, which is available to authorized users.
    Applied Microbiology and Biotechnology 04/2014; DOI:10.1007/s00253-014-5685-8 · 3.34 Impact Factor
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    • "Several inhibitors that target YycG in B subtilis, Staphylococcus aureus (S aureus), and S epidermidis have been documented to inhibit bacterial growth21, 22, 23. We previously described two inhibitors (Compounds 2 and 5) that target the HK domain of S epidermidis YycG and have bactericidal and biofilm-killing activities24. "
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    ABSTRACT: To evaluate the efficacies of six derivatives of Compound 2, a novel YycG histidine kinase inhibitor with the thiazolidione core structure in the treatment of medical device-related biofilm infections. The minimal inhibitory concentration (MIC) of the derivatives was determined using the macrodilution broth method, and the minimal bactericidal concentration (MBC) was obtained via sub-culturing 100 μL from each negative tube from the MIC assay onto drug-free Mueller-Hinton agar plates. Biofilm-killing effect for immature (6 h-old) biofilms was examined using a semiquantitative plate assay, and the effect on mature (24 h-old) biofilms was observed under a confocal laser scanning microscope (CLSM). The derivatives potently suppressed the growth of Staphylococcus epidermidis. The MIC values of the derivatives H2-10, H2-12, H2-20, H2-29, H2-27, and H2-28 on S epidermidis ATCC 35984 were 24.3, 6.5, 6.2, 3.3, 3.1, and 1.5 μg/mL, respectively. The MBC values of these derivatives were 48.6, 52.2, 12.4, 52.6, 12.4, and 6.2 μg/mL, respectively. The derivatives killed all bacteria in immature (6 h-old) biofilms and eliminated the biofilm proliferation. The derivatives also displayed strong bactericidal activities toward cells in mature (24 h-old) biofilms, whereas they showed low cytotoxicity and hemolytic activity toward Vero cells and human erythrocytes. The bactericidal and biofilm-killing activities of the new anti-YycG compounds were significantly better than the parent Compound 2.
    Acta Pharmacologica Sinica 03/2012; 33(3):418-25. DOI:10.1038/aps.2011.166 · 2.91 Impact Factor
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 06/2010; 41(27). DOI:10.1002/chin.201027195
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