JB
Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Kim, C.
Right arrow Articles by Dean, J. F. D.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Kim, C.
Right arrow Articles by Dean, J. F. D.

 Previous Article  |  Next Article 

Journal of Bacteriology, August 2001, p. 4866-4875, Vol. 183, No. 16
0021-9193/01/$04.00+0   DOI: 10.1128/JB.183.16.4866-4875.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

Oxidation of Phenolate Siderophores by the Multicopper Oxidase Encoded by the Escherichia coli yacK Gene

Chulhwan Kim, W. Walter Lorenz, J. Todd Hoopes, and Jeffrey F. D. Dean*

Daniel B. Warnell School of Forest Resources and Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602-2152

Received 12 March 2001/Accepted 31 May 2001

A gene (yacK) encoding a putative multicopper oxidase (MCO) was cloned from Escherichia coli, and the expressed enzyme was demonstrated to exhibit phenoloxidase and ferroxidase activities. The purified protein contained six copper atoms per polypeptide chain and displayed optical and electron paramagnetic resonance (EPR) spectra consistent with the presence of type 1, type 2, and type 3 copper centers. The strong optical A610 (E610 = 10,890 M-1 cm-1) and copper stoichiometry were taken as evidence that, similar to ceruloplasmin, the enzyme likely contains multiple type 1 copper centers. The addition of copper led to immediate and reversible changes in the optical and EPR spectra of the protein, as well as decreased thermal stability of the enzyme. Copper addition also stimulated both the phenoloxidase and ferroxidase activities of the enzyme, but the other metals tested had no effect. In the presence of added copper, the enzyme displayed significant activity against two of the phenolate siderophores utilized by E. coli for iron uptake, 2,3-dihydroxybenzoate and enterobactin, as well as 3-hydroxyanthranilate, an iron siderophore utilized by Saccharomyces cerevisiae. Oxidation of enterobactin produced a colored precipitate suggestive of the polymerization reactions that characterize microbial melanization processes. As oxidation should render the phenolate siderophores incapable of binding iron, yacK MCO activity could influence levels of free iron in the periplasm in response to copper concentration. This mechanism may explain, in part, how yacK MCO moderates the sensitivity of E. coli to copper.

* Corresponding author. Mailing address: School of Forest Resources, University of Georgia, Athens, GA 30602-2152. Phone: (706) 542-1710. Fax: (706) 542-8356. E-mail: jeffdean{at}uga.edu.

Journal of Bacteriology, August 2001, p. 4866-4875, Vol. 183, No. 16
0021-9193/01/$04.00+0   DOI: 10.1128/JB.183.16.4866-4875.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


This article has been cited by other articles:



Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
Appl. Environ. Microbiol. Infect. Immun. Eukaryot. Cell
Mol. Cell. Biol. J. Virol. Microbiol. Mol. Biol. Rev.
ALL ASM JOURNALS

Copyright © 2001 by the American Society for Microbiology. All rights reserved.