Study reveals copper-transporting function of yersiniabactin in bacteria

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Copper has been known to act as a toxin during bacterial infections; however, a recent study published in Nature Chemical Biology reveals that it could also play a dual role as a nutrient via the yersiniabactin (Ybt) system in Escherichia coli.

Initially, it was believed that Ybt operated as a siderophore but as co-author of the study, Jeffrey Henderson (Washington University School of Medicine, MO, USA), explained: “The traditional idea that yersiniabactin is an iron transporter is far too simplistic a view of this molecule.”

The researchers were able to demonstrate the nutritional properties of copper in the bacteria by using liquid chromatography–mass spectrometry  to measure the E. coli copper amine oxidase (TynA) levels – a copper-dependent cuproenzyme that catalyzes the conversion of phenylethylamine to phenylacetaldehyde. Their results indicated that E. coli could direct copper to cuproenzymes, which was “consistent with nutritional copper import by the Ybt metallophore system.”

Henderson also acknowledged that: “Bacteria that secrete yersiniabactin can bind to all sorts of metals. At the site of infection, this molecule appears to be grabbing onto metals all around it, preventing these metals from reaching toxic levels, but also bringing in controlled amounts of metal ions for nutritional purposes.”

The ability of Ybt to sequester copper to protect pathogenic Enterobacteriaceae during infections, as well as preserving its nutritional availability was also found to be analogous in fungal pathogens (Cryptococcus neoformans and Candida albicans). This suggests that other bacterial species may also exploit this strategy of nutritional preservation in order to survive, especially when metal ions are abundant.

The authors have also suggested roles for various cuproenzymes, which rely on copper importation by Ybt to form from their apo (inactive) to halo (active) forms – making Ybt an important virulence factor. They have concluded in their research that: “Further study is necessary to identify influential cuproenzymes that contribute to virulence during UTIs and other infections caused by Ybt-producing bacteria.”

Sources: Koh E-I, Robinson AE, Bandara N et al. Copper import in Esherichia coli by the yersiniabactin metallophore system. Nat. Chem. Biol. doi:10.1038/NCHEMBIO.2441 (2017) (Epub ahead of print); https://www.eurekalert.org/pub_releases/2017-07/wuso-aub072017.php

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