Functional Divergence of Heme-Thiolate Proteins: A Classification Based on Spectroscopic Attributes

Smith, Aaron T.; Pazicni, Samuel; Marvin, Katherine A.; Stevens, Daniel J.; Paulsen, Katherine M.; Burstyn, Judith N.

doi:10.1021/cr500056m

Cited by 49 publications

(81 citation statements)

References 319 publications

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“…The absorption spectrum shows a peak at 413 nm; a similar peak of lower intensity was observed in the absorption spectrum of the H648A mutant. As mentioned above, similar absorption patterns have been reported for heme binding to proteins with Cys/His coordination (Table S1), typical for low-spin type 2 heme thiolate Fe(III) Soret bands (15). Overall, these data are consistent with heme binding to the SUR2A subunit of the K ATP channel and are in agreement with the electrophysiology data.…”

Section: Resultssupporting

confidence: 88%

A heme-binding domain controls regulation of ATP-dependent potassium channels

Burton

Kapetanaki

Chernova

et al. 2016

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

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Heme iron has many and varied roles in biology. Most commonly it binds as a prosthetic group to proteins, and it has been widely supposed and amply demonstrated that subtle variations in the protein structure around the heme, including the heme ligands, are used to control the reactivity of the metal ion. However, the role of heme in biology now appears to also include a regulatory responsibility in the cell; this includes regulation of ion channel function. In this work, we show that cardiac K ATP channels are regulated by heme. We identify a cytoplasmic heme-binding CXXHX 16 H motif on the sulphonylurea receptor subunit of the channel, and mutagenesis together with quantitative and spectroscopic analyses of heme-binding and single channel experiments identified Cys628 and His648 as important for heme binding. We discuss the wider implications of these findings and we use the information to present hypotheses for mechanisms of heme-dependent regulation across other ion channels.heme | heme regulation | K ATP channel | SUR2A | potassium channel

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Section: Resultssupporting

confidence: 88%

A heme-binding domain controls regulation of ATP-dependent potassium channels

Burton

Kapetanaki

Chernova

et al. 2016

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

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“…6) and displays a low-spin ferric signal with g ϭ 3.09, 2.17, and 1.48, which is in good agreement with published data (37). The presence of a high-spin signal (g ϭ 6.0 and 1.99) could be due to the presence of a small population of Fe III -Ngb with a disulfide bridge between Cys 46 and Cys 55 , which promotes His 64 dissociation from the iron (38). In the presence of sulfide, a rhombic EPR signal was seen within 5 min with g ϭ 2.48, 2.21, and 1.85 (Fig.…”

Section: Epr Spectroscopysupporting

confidence: 89%

“…Additionally, with the H64A mutant, the heterogeneity could reflect the presence of a mixture of oxidized sulfur species coordinated to the ferric iron. Similar EPR spectra have been reported for the multiheme protein SoxXA involved in bacterial sulfur oxidation (55). The complexity in SoxXA spectrum arises from the simultaneous presence of three hemes that are coordinated by histidine on one side and to a thiol, persulfide, or methionine on the other (56).…”

Section: Cys-s-sh3 Cys-s-s-s-cysϩh 2 S Reactionsupporting

confidence: 70%

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A distal ligand mutes the interaction of hydrogen sulfide with human neuroglobin

Ruetz

Kumutima

Lewis

et al. 2017

Journal of Biological Chemistry

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Edited by Norma AllewellHydrogen sulfide is a critical signaling molecule, but high concentrations cause cellular toxicity. A four-enzyme pathway in the mitochondrion detoxifies H 2 S by converting it to thiosulfate and sulfate. Recent studies have shown that globins like hemoglobin and myoglobin can also oxidize H 2 S to thiosulfate and hydropolysulfides. Neuroglobin, a globin enriched in the brain, was reported to bind H 2 S tightly and was postulated to play a role in modulating neuronal sensitivity to H 2 S in conditions such as stroke. However, the H 2 S reactivity of the coordinately saturated heme in neuroglobin is expected a priori to be substantially lower than that of the 5-coordinate hemes present in myoglobin and hemoglobin. To resolve this discrepancy, we explored the role of the distal histidine residue in muting the reactivity of human neuroglobin toward H 2 S. Ferric neuroglobin is slowly reduced by H 2 S and catalyzes its inefficient oxidative conversion to thiosulfate. Mutation of the distal His 64 residue to alanine promotes rapid binding of H 2 S and its efficient conversion to oxidized products. X-ray absorption, EPR, and resonance Raman spectroscopy highlight the chemically different reaction options influenced by the distal histidine ligand. This study provides mechanistic insights into how the distal heme ligand in neuroglobin caps its reactivity toward H 2 S and identifies by cryo-mass spectrometry a range of sulfide oxidation products with 2-6 catenated sulfur atoms with or without oxygen insertion, which accumulate in the absence of the His 64 ligand.Neuroglobin is a member of the globin family (1) that is expressed primarily in neuronal tissues (2) but also in other metabolically highly active endocrine tissues, such as the adrenal gland and the pancreatic islets of Langerhans (3, 4). Although the physiological role of neuroglobin is still elusive, early studies suggested that it might be involved in oxygen supply (1, 5). However, neuroglobin is generally expressed at low levels and exhibits a high autoxidation rate, producing reactive oxygen species, which makes its role as an O 2 carrier unlikely (6). Neuroglobin can also scavenge reactive oxygen species and reduce nitrite to NO under hypoxic conditions (7-9).In contrast to hemoglobin and myoglobin, two histidine residues coordinate the heme cofactor in neuroglobin in the ferrous and ferric states (Fig. 1A). The crystal structure of neuroglobin reveals a high structural similarity to myoglobin, despite Ͻ25% amino acid sequence similarity between the proteins. The structure reveals a large hydrophobic cavity, which connects the proximal and distal sides of the heme (7). His 64 and His 96 coordinate the heme on the distal and proximal sides, respectively (10). Exogenous ligands like O 2 , CO, and NO bind to ferrous neuroglobin (Fe II -Ngb) 2 on the distal side, and binding is limited by dissociation of His 64 , which is slow (6,(11)(12)(13)(14). Limited characterization of the binding of sulfide to ferric neuroglobin (Fe III -Ngb) has...

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“…A number of heme-binding interactions have been suggested, including Cys/Pro (CP) motifs or Cys/His motifs (66,(68)(69)(70).…”

Section: Discussionmentioning

confidence: 99%

Regulation of intracellular heme trafficking revealed by subcellular reporters

Yuan

Rietzschel

Kwon

et al. 2016

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

109

126

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Heme is an essential prosthetic group in proteins that reside in virtually every subcellular compartment performing diverse biological functions. Irrespective of whether heme is synthesized in the mitochondria or imported from the environment, this hydrophobic and potentially toxic metalloporphyrin has to be trafficked across membrane barriers, a concept heretofore poorly understood. Here we show, using subcellular-targeted, genetically encoded hemoprotein peroxidase reporters, that both extracellular and endogenous heme contribute to cellular labile heme and that extracellular heme can be transported and used in toto by hemoproteins in all six subcellular compartments examined. The reporters are robust, show large signal-to-background ratio, and provide sufficient range to detect changes in intracellular labile heme. Restoration of reporter activity by heme is organelle-specific, with the Golgi and endoplasmic reticulum being important sites for both exogenous and endogenous heme trafficking. Expression of peroxidase reporters in Caenorhabditiselegans shows that environmental heme influences labile heme in a tissue-dependent manner; reporter activity in the intestine shows a linear increase compared with muscle or hypodermis, with the lowest heme threshold in neurons. Our results demonstrate that the trafficking pathways for exogenous and endogenous heme are distinct, with intrinsic preference for specific subcellular compartments. We anticipate our results will serve as a heuristic paradigm for more sophisticated studies on heme trafficking in cellular and whole-animal models.

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Functional Divergence of Heme-Thiolate Proteins: A Classification Based on Spectroscopic Attributes

Cited by 49 publications

References 319 publications

A heme-binding domain controls regulation of ATP-dependent potassium channels

A heme-binding domain controls regulation of ATP-dependent potassium channels

A distal ligand mutes the interaction of hydrogen sulfide with human neuroglobin

Regulation of intracellular heme trafficking revealed by subcellular reporters

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