title: Purification and characterization of the Staphylococcus aureus bacillithiol transferase BstA.
abstract: BACKGROUND
  Gram-positive bacteria in the phylum Firmicutes synthesize the low molecular weight thiol bacillithiol rather than glutathione or mycothiol. The bacillithiol transferase YfiT from Bacillus subtilis was identified as a new member of the recently discovered DinB/YfiT-like Superfamily. Based on structural similarity using the Superfamily program, we have determined 30 of 31 Staphylococcus aureus strains encode a single bacillithiol transferase from the DinB/YfiT-like Superfamily, while the remaining strain encodes two proteins.
  
  
  METHODS
  We have cloned, purified, and confirmed the activity of a recombinant bacillithiol transferase (henceforth called BstA) encoded by the S. aureus Newman ORF NWMN_2591. Moreover, we have studied the saturation kinetics and substrate specificity of this enzyme using in vitro biochemical assays.
  
  
  RESULTS
  BstA was found to be active with the co-substrate bacillithiol, but not with other low molecular weight thiols tested. BstA catalyzed bacillithiol conjugation to the model substrates monochlorobimane, 1-chloro-2,4-dinitrobenzene, and the antibiotic cerulenin. Several other molecules, including the antibiotic rifamycin S, were found to react directly with bacillithiol, but the addition of BstA did not enhance the rate of reaction. Furthermore, cells growing in nutrient rich medium exhibited low BstA activity.
  
  
  CONCLUSIONS
  BstA is a bacillithiol transferase from S. aureus that catalyzes the detoxification of cerulenin. Additionally, we have determined that bacillithiol itself might be capable of directly detoxifying electrophilic molecules.
  
  
  CONCLUSIONS
  BstA is an active bacillithiol transferase from S. aureus Newman and is the first DinB/YfiT-like Superfamily member identified from this organism. Interestingly, BstA is highly divergent from B. subtilis YfiT.
authors.affiliation: Division of Biological Sciences, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0377.
authors.forename: Varahenage R
authors.initials: VR
authors.lastname: Perera
authors.affiliation: Division of Biological Sciences, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0377.
authors.forename: Gerald L
authors.initials: GL
authors.lastname: Newton
authors.affiliation: Department of Chemistry and Biochemistry, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0378.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Parnell
authors.affiliation: Department of Chemistry and Biochemistry, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0378.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Komives
authors.affiliation: Division of Biological Sciences, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0377. Electronic address: kpogliano@ucsd.edu.
authors.forename: Kit
authors.initials: K
authors.lastname: Pogliano
mesh_terms: D001412:Bacillus subtilis / Q000201:enzymology; D001426:Bacterial Proteins / Q000737:chemistry / Q000302:isolation & purification; D002384:Catalysis; D002569:Cerulenin / Q000737:chemistry*; D004137:Dinitrochlorobenzene / Q000737:chemistry*; D011720:Pyrazoles / Q000737:chemistry*; D013211:Staphylococcus aureus / Q000201:enzymology*; D013379:Substrate Specificity; D014166:Transferases / Q000737:chemistry / Q000302:isolation & purification
chemical_list: D001426:Bacterial Proteins; D004137:Dinitrochlorobenzene; D011720:Pyrazoles; D002569:Cerulenin; C059597:monochlorobimane; D014166:Transferases
keywords: Staphylococcus aureus; bacillithiol; bacillithiol transferase; detoxification