Exploiting the conformational flexibility of leghemoglobin: a framework for examination of heme protein axial ligation

Patel, Neesha; Seward, Harriet E.; Svensson, Agneta; Gurman, S. J.; Thomson, Andrew J.; Raven, Emma Lloyd

doi:10.1016/s0003-9861(03)00403-x

Cited by 10 publications

(15 citation statements)

References 45 publications

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“…The absence of a 602 nm maximum in these spectra also suggests that Tyr B10 does not coordinate the iron when K53 is removed. 56 Interestingly, the spectra of ferric and ferrous wild-type and Y29F rTHB1 resemble those reported for the Met100Lys variant of cytochrome c 550 , 57 with allowance for a blue shift caused by the thioether cross-links in the cytochrome. Similarity to complexes with N–Fe–N coordination is also noted.…”

Section: Resultsmentioning

confidence: 62%

Characterization of THB1, a Chlamydomonas reinhardtii Truncated Hemoglobin: Linkage to Nitrogen Metabolism and Identification of Lysine as the Distal Heme Ligand

et al. 2014

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The nuclear genome of the model organism Chlamydomonas reinhardtii contains genes for a dozen hemoglobins of the truncated lineage. Of those, THB1 is known to be expressed, but the product and its function have not yet been characterized. We present mutagenesis, optical, and nuclear magnetic resonance data for the recombinant protein and show that at pH near neutral in the absence of added ligand, THB1 coordinates the heme iron with the canonical proximal histidine and a distal lysine. In the cyanomet state, THB1 is structurally similar to other known truncated hemoglobins, particularly the heme domain of Chlamydomonas eugametos LI637, a light-induced chloroplastic hemoglobin. Recombinant THB1 is capable of binding nitric oxide (NO•) in either the ferric or ferrous state and has efficient NO• dioxygenase activity. By using different C. reinhardtii strains and growth conditions, we demonstrate that the expression of THB1 is under the control of the NIT2 regulatory gene and that the hemoglobin is linked to the nitrogen assimilation pathway.

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Section: Resultsmentioning

confidence: 62%

Characterization of THB1, a Chlamydomonas reinhardtii Truncated Hemoglobin: Linkage to Nitrogen Metabolism and Identification of Lysine as the Distal Heme Ligand

et al. 2014

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“…In view of these possible distal conformations, an axial ligation scheme involving a tyrosine (Tyr22) seemed plausible in the absence of His46. Tyr involvement is observed in the Group I 2/2 Hb from Chlamydomonas eugametos (Tyr B10 aided by Lys E10) [49] and several other proteins, including engineered variants of sperm whale Mb [50] and leghemoglobin [51], and wild-type Paramphistomum epiclitum Mb [52][53][54]. In S6803 rHb, however, the optical spectra and the effect of the Tyr22 (B10) replacement were not consistent with Tyr ligation.…”

Section: Discussionmentioning

confidence: 95%

The role of the heme distal ligand in the post-translational modification of Synechocystis hemoglobin

Nothnagel

Love

Lecomte

2009

Journal of Inorganic Biochemistry

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“…Many aspects of the protein can be revealed by monitoring redox potential, such as bonding and electrostatic interactions at the redox center and conformational shifts associated with a change in oxidation state 21. All hxHbs (measured so far) have lower reduction potentials4, 22 than pentacoordinate Hbs,23, 24 and the degree to which this value is affected is related to the differential strength of His hx coordination in the ferric versus the ferrous oxidation state. Thus electrochemistry provides a corroborative complement to equilibrium binding in measuring whether the protein has evolved to augment the innate chemical tendency toward hexacoordination, or inhibit tight coordination to facilitate exogenous ligand‐binding.…”

Section: Introductionmentioning

confidence: 99%

Influence of the protein matrix on intramolecular histidine ligation in ferric and ferrous hexacoordinate hemoglobins

2006

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Present in most organisms, hexacoordinate hemoglobins (hxHbs) are proteins that have evolved the capacity for reversible bis-histidyl heme coordination. The heme prosthetic group enables diverse protein functionality, such as electron transfer, redox reactions, ligand transport, and enzymatic catalysis. The reactivity of heme is greatly effected by the coordination and noncovalent chemical environment imposed by its connate protein. Of considerable interest is how the hxHb globin fold achieves reversible intramolecular coordination while still enabling high-affinity binding of oxygen, nitric oxide, and other small ligands. Here we explore this question by examining the role of the protein matrix on coordination behavior in a group of hxHbs from animals, plants, and bacteria, including human neuroglobin and cytoglobin, a nonsymbiotic hemoglobin from rice, and a truncated hemoglobin from the cyanobacterium Synechocystis. This is done with a set of experiments measuring the reduction potentials of each wild-type hxHb and its corresponding mutant protein where the reversibly bound histidine (the distal His) has been replaced with a noncoordinating side chain. These reduction potentials, coupled with studies of the mutant proteins saturated with exogenous imidazole, enable us to assess the effects of the protein matrices on histidine coordination. Our results show significant variation among the hxHbs, demonstrating flexibility in the globin moiety's ability to regulate reversible coordination. This regulation is particularly evident in the plant nonsymbiotic hemoglobins, where ferric state histidine coordination affinity is substantially lowered by the protein matrix.

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Exploiting the conformational flexibility of leghemoglobin: a framework for examination of heme protein axial ligation

Cited by 10 publications

References 45 publications

Characterization of THB1, a Chlamydomonas reinhardtii Truncated Hemoglobin: Linkage to Nitrogen Metabolism and Identification of Lysine as the Distal Heme Ligand

Characterization of THB1, a Chlamydomonas reinhardtii Truncated Hemoglobin: Linkage to Nitrogen Metabolism and Identification of Lysine as the Distal Heme Ligand

The role of the heme distal ligand in the post-translational modification of Synechocystis hemoglobin

Influence of the protein matrix on intramolecular histidine ligation in ferric and ferrous hexacoordinate hemoglobins

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