Short-chain diamines are the physiological substrates of PACE family efflux pumps

Karl A. Hassan*, Varsha Naidu, Jacob R. Edgerton, Karla A. Mettrick, Qi Liu, Leila Fahmy, Liping Li, Scott M. Jackson, Irshad Ahmad, David Sharples, Peter J. F. Henderson, Ian T. Paulsen

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

Acinetobacter baumannii has rapidly emerged as a major cause of gram-negative hospital infections worldwide. A. baumannii encodes for the transport protein AceI, which confers resistance to chlorhexidine, a widely used antiseptic. AceI is also the prototype for the recently discovered proteobacterial antimicrobial compound efflux (PACE) family of transport proteins that confer resistance to a range of antibiotics and antiseptics in many gramnegative bacteria, including pathogens. The gene encoding AceI is conserved in the core genome of A. baumannii, suggesting that it has an important primordial function. This is incongruous with the sole characterized substrate of AceI, chlorhexidine, an entirely synthetic biocide produced only during the last century. Here we investigated a potential primordial function of AceI and other members of the PACE family in the transport of naturally occurring polyamines. Polyamines are abundant in living cells, where they have physiologically important functions and play multifaceted roles in bacterial infection. Gene expression studies revealed that the aceI gene is induced in A. baumannii by the short-chain diamines cadaverine and putrescine. Membrane transport experiments conducted in whole cells of A. baumannii and Escherichia coli and also in proteoliposomes showed that AceI mediates the efflux of these short-chain diamines when energized by an electrochemical gradient. Assays conducted using 8 additional diverse PACE family proteins identified 3 that also catalyze cadaverine transport. Taken together, these results demonstrate that shortchain diamines are common substrates for the PACE family of transport proteins, adding to their broad significance as a novel family of efflux pumps.

Original languageEnglish
Pages (from-to)18015-18020
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume116
Issue number36
DOIs
Publication statusPublished - 3 Sep 2019

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Keywords

  • drug resistance
  • polyamines
  • transport
  • efflux
  • PACE family

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