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Role of Glutathione in Buffering Excess Intracellular Copper in Streptococcus pyogenes

Stewart, Louisa J.; Ong, Cheryl-lynn Y.; Zhang, May M.; Brouwer, Stephan; McIntyre, Liam; Davies, Mark R.; Walker, Mark J.; McEwan, Alastair G.; Waldron, Kevin J.; Djoko, Karrera Y.

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Authors

Louisa J. Stewart

Cheryl-lynn Y. Ong

May M. Zhang

Stephan Brouwer

Liam McIntyre

Mark R. Davies

Mark J. Walker

Alastair G. McEwan

Kevin J. Waldron



Abstract

Copper (Cu) is an essential metal for bacterial physiology but in excess it is bacteriotoxic. To limit Cu levels in the cytoplasm, most bacteria possess a transcriptionally responsive system for Cu export. In the Gram-positive human pathogen Streptococcus pyogenes (group A Streptococcus [GAS]), this system is encoded by the copYAZ operon. This study demonstrates that although the site of GAS infection represents a Cu-rich environment, inactivation of the copA Cu efflux gene does not reduce virulence in a mouse model of invasive disease. In vitro, Cu treatment leads to multiple observable phenotypes, including defects in growth and viability, decreased fermentation, inhibition of glyceraldehyde-3-phosphate dehydrogenase (GapA) activity, and misregulation of metal homeostasis, likely as a consequence of mismetalation of noncognate metal-binding sites by Cu. Surprisingly, the onset of these effects is delayed by ∼4 h even though expression of copZ is upregulated immediately upon exposure to Cu. Further biochemical investigations show that the onset of all phenotypes coincides with depletion of intracellular glutathione (GSH). Supplementation with extracellular GSH replenishes the intracellular pool of this thiol and suppresses all the observable effects of Cu treatment. These results indicate that GSH buffers excess intracellular Cu when the transcriptionally responsive Cu export system is overwhelmed. Thus, while the copYAZ operon is responsible for Cu homeostasis, GSH has a role in Cu tolerance and allows bacteria to maintain metabolism even in the presence of an excess of this metal ion.

Citation

Stewart, L. J., Ong, C. Y., Zhang, M. M., Brouwer, S., McIntyre, L., Davies, M. R., …Djoko, K. Y. (2020). Role of Glutathione in Buffering Excess Intracellular Copper in Streptococcus pyogenes. mBio, 11(6), e02804-20. https://doi.org/10.1128/mbio.02804-20

Journal Article Type Article
Acceptance Date Oct 23, 2020
Online Publication Date Dec 1, 2020
Publication Date 2020
Deposit Date Dec 3, 2020
Publicly Available Date Dec 8, 2020
Journal mBio
Print ISSN 2161-2129
Publisher American Society for Microbiology
Peer Reviewed Peer Reviewed
Volume 11
Issue 6
Article Number e02804-20
Pages e02804-20
DOI https://doi.org/10.1128/mbio.02804-20

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