5lmc | pdb_00005lmc
Oxidized flavodiiron core of Escherichia coli flavorubredoxin, including the Fe-4SG atoms from its rubredoxin domain
Structural highlights
Function[NORV_ECOLI] Anaerobic nitric oxide reductase; uses NADH to detoxify nitric oxide (NO), protecting several 4Fe-4S NO-sensitive enzymes. Has at least 2 reductase partners, only one of which (NorW, flavorubredoxin reductase) has been identified. NO probably binds to the di-iron center; electrons enter from the reductase at rubredoxin and are transferred sequentially to the FMN center and the di-iron center. Also able to function as an aerobic oxygen reductase.[1] [2] Publication Abstract from PubMedFlavodiiron proteins (FDPs) are present in organisms from all domains of life and have been described so far to be involved in the detoxification of oxygen or nitric oxide, acting as O2 and/or NO reductases. The Escherichia coli FDP, named flavorubredoxin (FlRd) is the most extensively studied FDP. Biochemical and in vivo studies revealed that FlRd is involved in NO detoxification, as part of the bacterial defense mechanisms against reactive nitrogen species. E. coli FlRd has a clear preference for NO as substrate in vitro, exhibiting a very low reactivity towards O2. To contribute to the understanding of the structural features defining this substrate selectivity, we determined the crystallographic structure of E. coli FlRd, both in the as-isolated and reduced states. The overall tetrameric structure revealed a highly conserved flavodiiron core domain, with a metallo-beta-lactamase-like domain containing a diiron center and a flavodoxin domain with a FMN cofactor. The metal center in the oxidized state has a mu-hydroxo bridge coordinating the two irons, while in the reduced state this moiety is not detected. Since only the flavodiiron domain was observed in these crystal structures, the structure of the rubredoxin domain was determined by NMR. Tunnels for the substrates were identified, and through Molecular Dynamics simulations no differences for O2 or NO permeation were found. The present data represents the first structure for a NO-selective FDP. Structure of Escherichia coli Flavodiiron nitric oxide reductase.,Romao CV, Vicente JB, Borges PT, Victor BL, Lamosa P, Silva E, Pereira L, Bandeiras TM, Soares CM, Carrondo MA, Turner D, Teixeira M, Frazao C J Mol Biol. 2016 Oct 7. pii: S0022-2836(16)30423-5. doi:, 10.1016/j.jmb.2016.10.008. PMID:27725182[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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