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Abstract

is the most prevalent pathogen among all healthcare-associated infections. This anaerobic bacterium can colonize the human gut, typically following agents that disrupt the normal gut microbiota, like antibiotics. In the gut, is subjected to oxygen, which it has to eliminate for survival. Its genome encodes for two flavodiiron proteins, capable to reduce oxygen to water. Besides, some FDPs also reduce NO to N2O, an important feature as a resistance mechanism towards the human innate immune system [1,2]. Flavodiiron enzymes are constituted by a minimal core of two domains: a metallo-β-lactamase-like one, harboring the catalytic center, followed by a short-chain flavodoxin [1,2]. More complex FDPs exist, with multiple extra domains and redox centers [1,2]. contains a ‘classical’ FDP, and a very complex one, with an extra short-type rubredoxin domain followed by an NADH:rubredoxin oxidoreductase-like one [3]. The biochemical, redox and spectroscopic studies demonstrated that this enzyme receives electrons directly from NADH, reducing its substrates, precluding the need for extra partners. This FDP is selective for O2 (16s-1), almost 10x higher than with NO. The reactivity towards hydrogen peroxide, as an H2O2 reductase with formation of water, with a non-negligible turnover (2s-1) is a novelty in the field of FDPs. Site directed mutants revealed that the rubredoxin-like center is essential for electron transfer from NADH to the catalytic center.

[1] Martins et al, Free Rad. Biol. Med., in press, 2019.

[2] Romão et al, J. Biol.Inorg. Chem., 21,39-52, 2016.

[3] Folgosa et al, Sci.Rep., 8, 10164, 2018.

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/content/journal/acmi/10.1099/acmi.afm2019.po0017
2019-09-01
2019-10-15
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