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References

  1. Tortorella E, Tedesco P, Palma Esposito F, January G, Fani R, Jaspars M, et al. 2018. Antibiotics from deep-sea microorganisms:current discoveries and perspectives. Mar. Drugs 16. pii:E355.
    Pubmed PMC CrossRef
  2. Tyler PA. 2003. Ecosystems of the deep oceans, pp. 1-4. 1st Ed. Elsevier Science, Amsterdam.
  3. Wright PC, Westacott RE, Burja AM. 2003. Piezotolerance as a metabolic engineering tool for the biosynthesis of natural products. Biomol. Eng. 20: 325-331.
    Pubmed CrossRef
  4. Bull AT, Ward AC, Goodfellow M. 2000. Search and discovery strategies for biotechnology: the paradigm shift. Microbiol. Mol. Biol. Rev. 64: 573-606.
    Pubmed PMC CrossRef
  5. Blunt JW, Carroll AR, Copp BR, Davis RA, Keyzers RA, Prinsep MR. 2018. Marine natural products. Nat. Prod. Rep. 35: 8-53.
    Pubmed PMC CrossRef
  6. Braña AF, Sarmiento-Vizcaíno A, Pérez-Victoria I, Otero L, Fernández J, Palacios JJ, et al. 2017. Branimycins B and C, antibiotics produced by the abyssal actinobacterium Pseudonocardia carboxydivorans M-227. J. Nat. Prod. 80: 569-573.
    Pubmed CrossRef
  7. Le TC, Yang I, Yoon YJ, Nam SJ, Fenical W. 2016. Ansalactams B-D illustrate further biosynthetic plasticity within the ansamycin pathway. Org. Lett. 18: 2256-2259.
    Pubmed CrossRef
  8. Song Y, Li Q, Liu X, Chen Y, Zhang Y, Sun A, et al. 2014. Cyclic hexapeptides from the deep South China Sea-derived Streptomyces scopuliridis SCSIO ZJ46 active against pathogenic gram-positive bacteria. J. Nat. Prod. 77: 1937-1941.
    Pubmed CrossRef
  9. Pan HQ, Zhang SY, Wang N, Li ZL, Hua HM, Hu JC, et al. 2013. New spirotetronate antibiotics, lobophorins H and I, from a South China Sea-derived Streptomyces sp. 12A35. Mar. Drugs 11: 3891-3901.
    Pubmed PMC CrossRef
  10. Cossart P, Jonquières R. 2000. Sortase, a universal target for therapeutic agents against Gram-positive bacteria? Proc. Natl. Acad. Sci. USA 97: 5013-5015.
    Pubmed PMC CrossRef
  11. Mazmanian SK, Liu G, Jensen ER, Lenoy E, Schneewind O. 2000. Staphylococcus aureus sortase mutants defective in the display of surface proteins and in the pathogenesis of animal infections. Proc. Natl. Acad. Sci. USA 97: 5510-5515.
    Pubmed PMC CrossRef
  12. Wesson CA, Liou LE, Todd KM, Bohach GA, Trumble WR, Bayles KW. 1998. Staphylococcus aureus A grand Sar global regulators influence internalization and induction of apoptosis. Infect. Immun. 66: 5238-5243.
    Pubmed PMC CrossRef
  13. Mazmanian SK, Ton-That H, Su K, Schneewind O. 2002. An iron-regulated sortase anchors a class of surface protein during Staphylococcus aureus pathogenesis. Proc. Natl. Acad. Sci. USA 99: 2293-2298.
    Pubmed PMC CrossRef
  14. Mazmanian SK, Skaar EP, Gaspar AH, Humayun M, Gornicki P, Jelenska J, et al. 2003. Passage of heme-iron across the envelope of Staphylococcus aureus. Science 299: 906-909.
    Pubmed CrossRef
  15. Frankel BA, Bentley M, Kruger RG, McCafferty DG. 2004. Vinyl sulfones: inhibitors of SrtA, a transpeptidase required for cell wall protein anchoring and virulence in Staphylococcus aureus. J. Am. Chem. Soc. 126: 3404-3405.
    Pubmed CrossRef
  16. Sibbald MJ, Yang XM, Tsompanidou E, Qu D, Hecker M, Becher D, et al. 2012. Partially overlapping substrate specificities of staphylococcal group A sortases. Proteomics 12: 3049-3062.
    Pubmed CrossRef
  17. Cascioferro S, Raffa D, Maggio B, Raimondi MV, Schillaci D, Daidone G. 2015. Sortase A inhibitors: recent advances and future perspectives. J. Med. Chem. 58: 9108-9123.
    Pubmed CrossRef
  18. Kang H, Jensen PR, Fenical W. 1996. Isolation of microbial antibiotics from a marine ascidian of the genus Didemnum. J. Org. Chem. 61: 1543-1546.
    CrossRef
  19. Martínez-Luis S, Gómez JF, Spadafora C, Guzmán HM, Gutiérrez M. 2012. Antitrypanosomal alkaloids from the marine bacterium Bacillus pumilus. Molecules 17: 11146-11155.
    Pubmed PMC CrossRef
  20. Andrioli WJ, Lopes AA, Cavalcanti BC, Pessoa C, Nanayakkara NPD, Bastos JK. 2017. Isolation and characterization of 2pyridone alkaloids and alloxazines from Beauveria bassiana. Nat. Prod. Res. 31: 1920-1929.
    Pubmed CrossRef
  21. Lee KY, Shin DS, Yoon JM, Kang HJ, Oh KB. 2002. Expression of sortase, a transpeptidase for cell wall sorting reaction, from Staphylococcus aureus ATCC 6538p in Escherichia coli. J. Microbiol. Biotechnol. 12: 530-533.
  22. Oh KB, Kim SH, Lee J, Cho WJ, Lee T, Kim S. 2004. Discovery of diarylacrylonitriles as a novel series of small molecule sortase A inhibitors. J. Med. Chem. 47: 2418-2421.
    Pubmed CrossRef
  23. Hu P, Huang P, Chen WM. 2013. Curcumin inhibits the sortase A activity of the Streptococcus mutans UA159. Appl. Biochem. Biotechnol. 171: 396-402.
    Pubmed CrossRef
  24. Kim SH, Shin DS, Oh MN, Chung SC, Lee JS, Oh KB. 2004. Inhibition of the bacterial surface protein anchoring transpeptidase sortase by isoquinoline alkaloids. Biosci. Biotechnol. Biochem. 68: 421-424.
    Pubmed CrossRef
  25. Jonsson M, Mazmanian SK, Schneewind O, Bremell T, Tarkowski A. 2003. The role of Staphylococcus aureus sortase A and sortase B in murine arthritis. Microbes Infect. 5: 775-780.
    Pubmed CrossRef
  26. Weinstein MP, Limbago B, Patel JB, Mathers AJ, Burnham C, Mazzulli T, et al. 2018. Methods for Dilution Antimicrobial Susceptibility Test for Bacteria That Grow aerobically, pp. 15-50. 11th Ed. Clinical and Laboratory Standards Institute, Wayne, Pennsylvania.
  27. Lineweaver H, Burk D. 1934. The determination of enzyme dissociation constants. J. Am. Chem. Soc. 56: 658-666.
    CrossRef
  28. Alksne LE, Projan SJ. 2000. Bacterial virulence as a target for antimicrobial chemotherapy. Curr. Opin. Biotechnol. 11: 625-636.
    Pubmed CrossRef
  29. Zhang B, Teng Z, Li X, Lu G, Deng X, Niu X, Wang J. 2017. Chalcone attenuates Staphylococcus aureus virulence by targeting sortase A and alpha-hemolysin. Front. Microbiol. 8: 1715.
    Pubmed PMC CrossRef
  30. Weiss WJ, Lenoy E, Murphy T, Tardio L, Burgio P, Projan SJ, et al. 2004. Effect of srtA and srtB gene expression on the virulence of Staphylococcus aureus in animal models of infection. J. Antimicrob. Chemother. 53: 480-486.
    Pubmed CrossRef

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Note

J. Microbiol. Biotechnol. 2019; 29(10): 1603-1606

Published online October 28, 2019 https://doi.org/10.4014/jmb.1906.06026

Copyright © The Korean Society for Microbiology and Biotechnology.

Inhibitory Effects of Streptomyces sp. MBTH32 Metabolites on Sortase A and Sortase A-Mediated Cell Clumping of Staphylococcus aureus to Fibrinogen

Beomkoo Chung 1, Oh-Seok Kwon 2, Jongheon Shin 2* and Ki-Bong Oh 1*

1Department of Agricultural Biotechnology, College of Agriculture and Life Sciences, Seoul National University, Seoul 08826, Republic of Korea, 2Natural Products Research Institute, College of Pharmacy, Seoul National University, Seoul 08826, Republic of Korea

Correspondence to:Jongheon Shin    shinj@snu.ac.kr
Ki-Bong Oh    ohkibong@snu.ac.kr

Received: June 13, 2019; Accepted: August 28, 2019

Abstract

Sortase A (SrtA), a type of transpeptidase responsible for anchoring surface proteins to the peptidoglycan cell wall, is important in the virulence of gram-positive bacteria. Three compounds were isolated from marine-derived Streptomyces sp. MBTH32 using various chromatography techniques. The structures of these compounds were determined based on spectroscopic data and comparisons with previously reported data. Among the metabolites tested, lumichrome showed strong inhibitory activity against Staphylococcus aureus SrtA without affecting cell viability. The results of cell clumping activity assessment suggest the potential for using this compound to treat S. aureus infection by inhibiting SrtA activity.

Keywords: Marine Streptomyces, lumichrome, Staphylococcus aureus, sortase A, cell clumping

Body

The ocean environment covers 70% of the Earth’s surface and has more diverse conditions than the terrestrial environment, such as low oxygen and lack of light [1, 2]. Under these conditions, biosynthesis of secondary metabolites typically involves mechanisms modified for physiological adaptation, which increases the probability that unusual natural products might be present [3, 4]. In the last decade, numerous natural products have been discovered in the marine environment; notably, thousands of those compounds exhibit new structures, and three-fourths of them demonstrate diverse bioactivities [5]. Marine-derived Streptomyces species have been identified as major producers of novel antibiotics, such as branimycins B and C [6]; ansalactams B, C, and D [7]; desotamide B [8]; and lobophorin H [9]. Thus, marine-derived Streptomyces species could be outstanding sources of novel antimicrobial agents.

Sortases, transpeptidases that anchor surface proteins to the peptidoglycan layer in gram-positive bacteria, have attracted attention as a potential target of novel antibiotics [10]. Surface proteins covalently tethered to the cell wall by sortases allow gram-positive bacteria to adhere to host tissues and to invade epithelial cells [11, 12]. Sortases comprise six isoforms, A–F (SrtA–F). Among them, SrtA has been shown to play an important role in the pathogenesis of S. aureus via gene knockout experiments [13, 14]. Indeed, S. aureus mutants lacking SrtA were limited in their abilities to make biofilms and infect host cells maintaining cell viability. The effective pharmacophores against SrtA were recently researched and morpholino benzoate, thiazolidine derivatives were identified as promising SrtA inhibitors [15-17].

In our search for SrtA inhibitors in marine-derived Actinomycetes, we found that an ethyl acetate extraction of Streptomyces strain MBTH32 exhibited moderate activity against S. aureus SrtA (IC50 = 64.27 μg/ml). Stepwise separation of the crude extract using various chromatography methods yielded three compounds with SrtA inhibitory activity. The structures of these compounds were determined by extensive spectroscopic analyses. Herein we report the potential of these compounds for inhibition of SrtA and SrtA-mediated cell clumping in S. aureus.

Strain MBTH32 was isolated from marine sediment from Shinjin Island, Republic of Korea; it showed 98% identity to Streptomyces longispororuber and was therefore designated Streptomyces sp. MBTH32 (GenBank accession number: MK840992). Strain MBTH32 was cultured in yeast–peptone–mannitol (YPM) medium (2 g yeast extract, 2 g peptone, 4 g mannitol, and 23 g sea salt in 1 L distilled water) at 28°C for 7 days on a rotary shaker. It was then filtered and extracted with an equal volume of ethyl acetate; this was performed twice. The ethyl acetate fraction was incrassated and 1.6 g of dried material was obtained for biological and chemical assays. The entire extract was separated by C18 reversed-phase vacuum flash column chromatography using serial dilutions of methanol and water as eluents. Based on the results of the SrtA inhibition assay, the fraction eluted in 20% aqueous methanol was isolated by reversed-phase high-performance liquid chromatography (Agilent Eclipse XDB-C18, 5 μm, 9.4 × 250 mm) to yield compounds 1–3. A total of 14.6 mg, 3.6 mg, and 3.5 mg of compounds 1, 2, and 3 were purified. The structures of these compounds, designated as enterocin (1) [18], N-acetyl-β-oxotryptamine (2) [19], and lumichrome (3) [20], were determined based on the results of spectroscopic analyses and comparisons with previously reported data (Fig. 1).

Figure 1. Structures of compounds 1–3 isolated from marinederived Streptomyces sp. MBTH32: enterocin (1), N-acetyl-β-oxotryptamine (2), and lumichrome (3).

Recombinant SrtA was purified from transformed Escherichia coli by nickel-based affinity chromatography [21]. Inhibitory activity against SrtA was determined by quantifying the intensity of augmented fluorescence upon cleavage of a synthetic peptide containing LPETG motifs. Fluorescence induced from tested compounds was excluded to avoid interference with substrate [22, 23]. SrtA suppression abilities of isolated compounds and berberine chloride, a known SrtA inhibitor [24], were estimated with IC50 values (half maximal inhibitory concentrations)(Table 1). Compounds 1 and 2 exhibited weak SrtA inhibitory activity. In contrast, compound 3 significantly inhibited SrtA, with an IC50 value of 198.20 μM. SrtA inhibitors that do not hinder microbial viability are considered to be more valuable therapeutic agents [25]. Therefore, we investigated the efficacies of these three compounds on bacterial growth using the minimum inhibitory concentration assay [26]. As shown in Table 1, compounds 2 and 3 displayed no growth inhibition activity against S. aureus. However, the inhibition pattern of compound 3, as determined using the Lineweaver-Burk plot method [27] (Ki = 0.91 mM), indicated that it served as a competitive inhibitor (Fig. 2).

Table 1 . Inhibitory effects of compounds 1–3 on the activity of SrtA and bacterial growth of S. aureus ATCC6538p..

CompoundIC50 (μM)MIC (μM)


SrtAS. aureus ATCC6538p
1594.76 ± 3.789.00
21108.65 ± 7.52>1185.19
3198.20 ± 0.94>528.42
Berberine chloride106.40 ± 1.36>344.26

Berberine chloride was used as a reference inhibitor of SrtA. IC50 values are the mean ± SD (n = 3)..


Figure 2. Lineweaver-Burk plot of SrtA inhibition by compound 3. Compound 3 was applied at IC50 and at 2× IC50 concentrations. [S], reaction substrate concentration; V, reaction velocity (Δfluorescence/ min). Each point indicates the mean ± SD of three independent experiments.

SrtA has been reported to immobilize fibrinogen-binding protein, thus accelerating bacterial adhesion to host tissues and subsequent invasion [28, 29]. We hypothesized that the immobilization of fibrinogen-binding protein may be reduced by suppression of SrtA activity in vivo. To confirm our assumption, S. aureus Newman (wild-type) and SKM12 (srtA-) strains were used in SrtA-mediated cell clumping to fibrinogen [30]. Cells were centrifuged and resuspended with fibrinogen solution. Absorbance at 600 nm was measured for each sample at 0 h and 2 h after resuspension. The data are shown as the absorbance (mean ± SD, three independent experiments) at 2 h, divided by absorbance at time zero, multiplied by 100. Whereas the wild-type strain showed >70% reduction in absorbance at 600 nm after 2 h incubation, the srtA-knockout mutant only showed 20%reduction in absorbance after a similar period of incubation; this indicates that SrtA plays a crucial role in anchoring the clumping factor to the cell wall (Fig. 3A). The clumping abilities of the wild-type strain treated with various concentrations of compound 3 were also measured and compared with its clumping ability when treated with berberine chloride. The ability of the wild-type strain to develop SrtA-mediated clumps was reduced in a dose-dependent manner upon treatment with compound 3. In particular, the absorbance of a sample treated with 100 μM compound 3 for 2 h was estimated to be 60% of the initial value, which was slightly lower than the absorbance when treated with an outstanding inhibitor, berberine chloride (Fig. 3B). These data suggest that compound 3 directly targets SrtA and decreases pathogenicity by inhibiting covalent linkage of surface proteins to the peptidoglycan layer in S. aureus.

Figure 3. Effects of srtA gene expression and SrtA inhibitors on the clumping of S. aureus with fibrinogen. (A) Clumping assay was performed with S. aureus Newman (wild-type) and SKM12 (srtA-knockout mutant) strains. (B) Berberine chloride and compound 3 were applied at the indicated concentrations at 37°C for 2 h. The t-test was used for statistical analysis of multiple comparisons. A value of p < 0.05 was used as the criterion for statistical significance. *p < 0.05, **p < 0.01, ***p < 0.001.

In conclusion, three metabolites isolated from marine-derived Streptomyces sp. MBTH32 displayed inhibitory activity against S. aureus SrtA. Among them, lumichrome (compound 3) showed the greatest activity against SrtA without affecting microbial growth. The SrtA-mediated clumping assay demonstrated that SrtA is responsible for covalent linkage of surface proteins to the cell wall. It also indicated that compound 3 may be useful in the treatment of S. aureus infections by inhibiting the anchoring ability of SrtA. These findings may be valuable for novel antibiotic research and may facilitate studies of structure-related activities among similar SrtA inhibitors.

Acknowledgments

This research was supported by the Basic Science Research Program through the National Research Foundation (NRF-2018R1D1A1B07043375) of Korea funded by the Ministry of Education, Science and Technology.

Conflict of Interest

The authors have no financial conflicts of interest to declare.

Fig 1.

Figure 1.Structures of compounds 1–3 isolated from marinederived Streptomyces sp. MBTH32: enterocin (1), N-acetyl-β-oxotryptamine (2), and lumichrome (3).
Journal of Microbiology and Biotechnology 2019; 29: 1603-1606https://doi.org/10.4014/jmb.1906.06026

Fig 2.

Figure 2.Lineweaver-Burk plot of SrtA inhibition by compound 3. Compound 3 was applied at IC50 and at 2× IC50 concentrations. [S], reaction substrate concentration; V, reaction velocity (Δfluorescence/ min). Each point indicates the mean ± SD of three independent experiments.
Journal of Microbiology and Biotechnology 2019; 29: 1603-1606https://doi.org/10.4014/jmb.1906.06026

Fig 3.

Figure 3.Effects of srtA gene expression and SrtA inhibitors on the clumping of S. aureus with fibrinogen. (A) Clumping assay was performed with S. aureus Newman (wild-type) and SKM12 (srtA-knockout mutant) strains. (B) Berberine chloride and compound 3 were applied at the indicated concentrations at 37°C for 2 h. The t-test was used for statistical analysis of multiple comparisons. A value of p < 0.05 was used as the criterion for statistical significance. *p < 0.05, **p < 0.01, ***p < 0.001.
Journal of Microbiology and Biotechnology 2019; 29: 1603-1606https://doi.org/10.4014/jmb.1906.06026

Table 1 . Inhibitory effects of compounds 1–3 on the activity of SrtA and bacterial growth of S. aureus ATCC6538p..

CompoundIC50 (μM)MIC (μM)


SrtAS. aureus ATCC6538p
1594.76 ± 3.789.00
21108.65 ± 7.52>1185.19
3198.20 ± 0.94>528.42
Berberine chloride106.40 ± 1.36>344.26

Berberine chloride was used as a reference inhibitor of SrtA. IC50 values are the mean ± SD (n = 3)..


References

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    Pubmed KoreaMed CrossRef
  2. Tyler PA. 2003. Ecosystems of the deep oceans, pp. 1-4. 1st Ed. Elsevier Science, Amsterdam.
  3. Wright PC, Westacott RE, Burja AM. 2003. Piezotolerance as a metabolic engineering tool for the biosynthesis of natural products. Biomol. Eng. 20: 325-331.
    Pubmed CrossRef
  4. Bull AT, Ward AC, Goodfellow M. 2000. Search and discovery strategies for biotechnology: the paradigm shift. Microbiol. Mol. Biol. Rev. 64: 573-606.
    Pubmed KoreaMed CrossRef
  5. Blunt JW, Carroll AR, Copp BR, Davis RA, Keyzers RA, Prinsep MR. 2018. Marine natural products. Nat. Prod. Rep. 35: 8-53.
    Pubmed KoreaMed CrossRef
  6. Braña AF, Sarmiento-Vizcaíno A, Pérez-Victoria I, Otero L, Fernández J, Palacios JJ, et al. 2017. Branimycins B and C, antibiotics produced by the abyssal actinobacterium Pseudonocardia carboxydivorans M-227. J. Nat. Prod. 80: 569-573.
    Pubmed CrossRef
  7. Le TC, Yang I, Yoon YJ, Nam SJ, Fenical W. 2016. Ansalactams B-D illustrate further biosynthetic plasticity within the ansamycin pathway. Org. Lett. 18: 2256-2259.
    Pubmed CrossRef
  8. Song Y, Li Q, Liu X, Chen Y, Zhang Y, Sun A, et al. 2014. Cyclic hexapeptides from the deep South China Sea-derived Streptomyces scopuliridis SCSIO ZJ46 active against pathogenic gram-positive bacteria. J. Nat. Prod. 77: 1937-1941.
    Pubmed CrossRef
  9. Pan HQ, Zhang SY, Wang N, Li ZL, Hua HM, Hu JC, et al. 2013. New spirotetronate antibiotics, lobophorins H and I, from a South China Sea-derived Streptomyces sp. 12A35. Mar. Drugs 11: 3891-3901.
    Pubmed KoreaMed CrossRef
  10. Cossart P, Jonquières R. 2000. Sortase, a universal target for therapeutic agents against Gram-positive bacteria? Proc. Natl. Acad. Sci. USA 97: 5013-5015.
    Pubmed KoreaMed CrossRef
  11. Mazmanian SK, Liu G, Jensen ER, Lenoy E, Schneewind O. 2000. Staphylococcus aureus sortase mutants defective in the display of surface proteins and in the pathogenesis of animal infections. Proc. Natl. Acad. Sci. USA 97: 5510-5515.
    Pubmed KoreaMed CrossRef
  12. Wesson CA, Liou LE, Todd KM, Bohach GA, Trumble WR, Bayles KW. 1998. Staphylococcus aureus A grand Sar global regulators influence internalization and induction of apoptosis. Infect. Immun. 66: 5238-5243.
    Pubmed KoreaMed CrossRef
  13. Mazmanian SK, Ton-That H, Su K, Schneewind O. 2002. An iron-regulated sortase anchors a class of surface protein during Staphylococcus aureus pathogenesis. Proc. Natl. Acad. Sci. USA 99: 2293-2298.
    Pubmed KoreaMed CrossRef
  14. Mazmanian SK, Skaar EP, Gaspar AH, Humayun M, Gornicki P, Jelenska J, et al. 2003. Passage of heme-iron across the envelope of Staphylococcus aureus. Science 299: 906-909.
    Pubmed CrossRef
  15. Frankel BA, Bentley M, Kruger RG, McCafferty DG. 2004. Vinyl sulfones: inhibitors of SrtA, a transpeptidase required for cell wall protein anchoring and virulence in Staphylococcus aureus. J. Am. Chem. Soc. 126: 3404-3405.
    Pubmed CrossRef
  16. Sibbald MJ, Yang XM, Tsompanidou E, Qu D, Hecker M, Becher D, et al. 2012. Partially overlapping substrate specificities of staphylococcal group A sortases. Proteomics 12: 3049-3062.
    Pubmed CrossRef
  17. Cascioferro S, Raffa D, Maggio B, Raimondi MV, Schillaci D, Daidone G. 2015. Sortase A inhibitors: recent advances and future perspectives. J. Med. Chem. 58: 9108-9123.
    Pubmed CrossRef
  18. Kang H, Jensen PR, Fenical W. 1996. Isolation of microbial antibiotics from a marine ascidian of the genus Didemnum. J. Org. Chem. 61: 1543-1546.
    CrossRef
  19. Martínez-Luis S, Gómez JF, Spadafora C, Guzmán HM, Gutiérrez M. 2012. Antitrypanosomal alkaloids from the marine bacterium Bacillus pumilus. Molecules 17: 11146-11155.
    Pubmed KoreaMed CrossRef
  20. Andrioli WJ, Lopes AA, Cavalcanti BC, Pessoa C, Nanayakkara NPD, Bastos JK. 2017. Isolation and characterization of 2pyridone alkaloids and alloxazines from Beauveria bassiana. Nat. Prod. Res. 31: 1920-1929.
    Pubmed CrossRef
  21. Lee KY, Shin DS, Yoon JM, Kang HJ, Oh KB. 2002. Expression of sortase, a transpeptidase for cell wall sorting reaction, from Staphylococcus aureus ATCC 6538p in Escherichia coli. J. Microbiol. Biotechnol. 12: 530-533.
  22. Oh KB, Kim SH, Lee J, Cho WJ, Lee T, Kim S. 2004. Discovery of diarylacrylonitriles as a novel series of small molecule sortase A inhibitors. J. Med. Chem. 47: 2418-2421.
    Pubmed CrossRef
  23. Hu P, Huang P, Chen WM. 2013. Curcumin inhibits the sortase A activity of the Streptococcus mutans UA159. Appl. Biochem. Biotechnol. 171: 396-402.
    Pubmed CrossRef
  24. Kim SH, Shin DS, Oh MN, Chung SC, Lee JS, Oh KB. 2004. Inhibition of the bacterial surface protein anchoring transpeptidase sortase by isoquinoline alkaloids. Biosci. Biotechnol. Biochem. 68: 421-424.
    Pubmed CrossRef
  25. Jonsson M, Mazmanian SK, Schneewind O, Bremell T, Tarkowski A. 2003. The role of Staphylococcus aureus sortase A and sortase B in murine arthritis. Microbes Infect. 5: 775-780.
    Pubmed CrossRef
  26. Weinstein MP, Limbago B, Patel JB, Mathers AJ, Burnham C, Mazzulli T, et al. 2018. Methods for Dilution Antimicrobial Susceptibility Test for Bacteria That Grow aerobically, pp. 15-50. 11th Ed. Clinical and Laboratory Standards Institute, Wayne, Pennsylvania.
  27. Lineweaver H, Burk D. 1934. The determination of enzyme dissociation constants. J. Am. Chem. Soc. 56: 658-666.
    CrossRef
  28. Alksne LE, Projan SJ. 2000. Bacterial virulence as a target for antimicrobial chemotherapy. Curr. Opin. Biotechnol. 11: 625-636.
    Pubmed CrossRef
  29. Zhang B, Teng Z, Li X, Lu G, Deng X, Niu X, Wang J. 2017. Chalcone attenuates Staphylococcus aureus virulence by targeting sortase A and alpha-hemolysin. Front. Microbiol. 8: 1715.
    Pubmed KoreaMed CrossRef
  30. Weiss WJ, Lenoy E, Murphy T, Tardio L, Burgio P, Projan SJ, et al. 2004. Effect of srtA and srtB gene expression on the virulence of Staphylococcus aureus in animal models of infection. J. Antimicrob. Chemother. 53: 480-486.
    Pubmed CrossRef