Nonsteric factors dominate binding of nitric oxide, azide, imidazole, cyanide, and fluoride to the Rhizobial heme-based oxygen sensor FixL

Winkler, William E.; González, Gonzalo; Wittenberg, Jonathan B.; Hille, Russ; Dakappagari, Naveen; Jacob, Anand; Gonzalez, Leyla A.; Gilles-Gonzalez, Marie-Alda

doi:10.1016/s1074-5521(96)90070-8

Cited by 55 publications

(61 citation statements)

References 24 publications

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“…ref. 25) and is consistent with ferric FixLH being five-coordinate unliganded (14,26). Transient spectra of unliganded ferrous FixLH are similar to those of reduced unliganded Mb (27) and GC (6) and mainly reflect the heme photophysics, which can be understood in the framework of two excited states cascading back to the ground state (28,29).…”

Section: Resultssupporting

confidence: 63%

Ultrafast ligand rebinding in the heme domain of the oxygen sensors FixL and Dos: General regulatory implications for heme-based sensors

Liebl

Bouzhir-Sima

Négrerie

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

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Heme-based oxygen sensors are part of ligand-specific twocomponent regulatory systems, which have both a relatively low oxygen affinity and a low oxygen-binding rate. To get insight into the dynamical aspects underlying these features and the ligand specificity of the signal transduction from the heme sensor domain, we used femtosecond spectroscopy to study ligand dynamics in the heme domains of the oxygen sensors FixL from Bradyrhizobium japonicum (FixLH) and Dos from Escherichia coli (DosH). The heme coordination with different ligands and the corresponding ground-state heme spectra of FixLH are similar to myoglobin (Mb). After photodissociation, the excited-state properties and ligand-rebinding kinetics are qualitatively similar for FixLH and Mb for CO and NO as ligands. In contrast to Mb, the transient spectra of FixLH after photodissociation of ligands are distorted compared with the ground-state difference spectra, indicating differences in the heme environment with respect to the unliganded state. This distortion is particularly marked for O 2. Strikingly, heme-O 2 recombination occurs with efficiency unprecedented for heme proteins, in Ϸ5 ps for Ϸ90% of the dissociated O2. For DosH-O2, which shows 60% sequence similarity to FixLH, but where signal detection and transmission presumably are quite different, a similarly fast recombination was found with an even higher yield. Altogether these results indicate that in these sensors the heme pocket acts as a ligand-specific trap. The general implications for the functioning of heme-based ligand sensors are discussed in the light of recent studies on heme-based NO and CO sensors.

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Section: Resultssupporting

confidence: 63%

Ultrafast ligand rebinding in the heme domain of the oxygen sensors FixL and Dos: General regulatory implications for heme-based sensors

Liebl

Bouzhir-Sima

Négrerie

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

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“…M for BjFixLH) (15,31). Comparison of the met and cyanomet forms shows distinct changes within this heme-binding domain.…”

Section: ϫ4mentioning

confidence: 96%

Structure of a biological oxygen sensor: A new mechanism for heme-driven signal transduction

Gong

Hao

Mansy

et al. 1998

Proc. Natl. Acad. Sci. U.S.A.

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371

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The FixL proteins are biological oxygen sensors that restrict the expression of specific genes to hypoxic conditions. FixL's oxygen-detecting domain is a heme binding region that controls the activity of an attached histidine kinase. The FixL switch is regulated by binding of oxygen and other strong-field ligands. In the absence of bound ligand, the heme domain permits kinase activity. In the presence of bound ligand, this domain turns off kinase activity. Comparison of the structures of two forms of the Bradyrhizobium japonicum FixL heme domain, one in the ''on'' state without bound ligand and one in the ''off'' state with bound cyanide, reveals a mechanism of regulation by a heme that is distinct from the classical hemoglobin models. The close structural resemblance of the FixL heme domain to the photoactive yellow protein confirms the existence of a PAS structural motif but reveals the presence of an alternative regulatory gateway.

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“…FixL, a chimeric protein having a haem domain and a kinase domain, occurring in Rhizobium or Bradyrhizobium binds oxygen reversibly with a very low affinity. The proposed function of this protein (function 6) is to sense oxygen through its haem domain and transduce this signal by controlling the phosphorylation of the transcriptional activator FixJ that in turn induces the expression of nitrogen fixation genes, thereby enabling oxygen-dependent switching of nitrogen fixation [23][24][25]. Chimeric two-domain O 2 -binding proteins are found in other bacteria: the flavohaemoglobins in yeast [26,27] and the hydrogen bacterium, Alcaligenes eutrophus [28], show a diaphorase activity, whereas that of Escherichia coli [29] shows a dihydropteridine reductase activity.…”

Section: Physiological Functionsmentioning

confidence: 99%

Evolution of myoglobin

Suzuki

Imai

1998

CMLS, Cell. Mol. Life Sci.

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The distribution, physiological function, amino acid sequence and gene structure of myoglobin and myoglobin-like proteins from various taxa are summarized, and their evolution is discussed. Although it has long been thought that all haemoglobins and myoglobins have evolved from a common ancestral gene, the knowledge presently accumulated about the structures of these proteins suggests that there may be three distinct origins: a 'universal globin', a 'compact globin' and an 'IDO-like globin'.

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Nonsteric factors dominate binding of nitric oxide, azide, imidazole, cyanide, and fluoride to the Rhizobial heme-based oxygen sensor FixL

Cited by 55 publications

References 24 publications

Ultrafast ligand rebinding in the heme domain of the oxygen sensors FixL and Dos: General regulatory implications for heme-based sensors

Ultrafast ligand rebinding in the heme domain of the oxygen sensors FixL and Dos: General regulatory implications for heme-based sensors

Structure of a biological oxygen sensor: A new mechanism for heme-driven signal transduction

Evolution of myoglobin

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