title: Bacterial thioredoxin and thioredoxin reductase as mediators for epigallocatechin 3-gallate-induced antimicrobial action.
abstract: Epigallocatechin 3-gallate (EGCG) is the most abundant catechin in green tea and may combat bacteria with few side-effects. Its selectivity for different bacterial infections remains unclear, and hence the identification of the underlying mechanism is of practical importance. Both the thioredoxin (Trx) system and the glutathione/glutaredoxin (Grx) system support bacterial growth. Some pathogenic bacteria are naturally deficient in the Grx system. We analyzed the effect of green tea extract (GTE) and EGCG on wild-type and null mutants of Escherichia coli with either Trx or Grx system deficiency and found that GTE and EGCG selected the Trx system as a target and killed the mutant that is exclusively dependent on Trx/Trx reductase (TrxR). EGCG inhibited the activity of both Trx1 and TrxR of E. coli in a dose-dependent and time-dependent manner. The IC50 values of EGCG for the reduced forms of E. coli Trx1/TrxR were ~ 3-4-fold lower than those for their non-reduced forms. The IC50 value of EGCG for the E. coli Trx1 system was 56-fold lower than that for the mammalian Trx1 system. The inhibition by EGCG of both Trx1 and TrxR of E. coli was irreversible. EGCG-induced inactivation of E. coli Trx1 was a second-order process, and that of E. coli TrxR was an affinity-labeling process. The covalent binding sites for EGCG in E. coli Trx1 were Trp(28) , Trp(31) and Cys(32) , and in E. coli TrxR were Cys(135) and Cys(138) . Moreover, the sensitivity of Staphylococcus aureus to EGCG was similar to that of an E. coli mutant with Grx system deficiency. EGCG-induced inactivation of Trx/TrxR in S. aureus coincided with suppressed growth of this virulent pathogen. Our findings suggest a role for EGCG-dependent Trx/TrxR inactivation in potentiating antibacterial activity of EGCG.
authors.affiliation: College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Liang
authors.affiliation: Division of Biochemistry, Department of Medical Biochemistry and Biophysics, Karolinska Institute, Stockholm, Sweden.
authors.forename: Aristi P
authors.initials: AP
authors.lastname: Fernandes
authors.affiliation: Division of Biochemistry, Department of Medical Biochemistry and Biophysics, Karolinska Institute, Stockholm, Sweden.
authors.forename: Arne
authors.initials: A
authors.lastname: Holmgren
authors.affiliation: The State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Li
authors.affiliation: College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China.
authors.forename: Liangwei
authors.initials: L
authors.lastname: Zhong
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology*; D002392:Catechin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D009154:Mutation; D013211:Staphylococcus aureus / Q000187:drug effects / Q000254:growth & development; D013329:Structure-Activity Relationship; D013880:Thioredoxin-Disulfide Reductase / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D013879:Thioredoxins / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents; D013879:Thioredoxins; D002392:Catechin; C045651:epigallocatechin gallate; D013880:Thioredoxin-Disulfide Reductase
keywords: antibiotics; epigallocatechin 3-gallate; glutaredoxin; green tea; thioredoxin