Novel Histidine−Heme Covalent Linkage in a Hemoglobin

Vu, B. Christie; Jones, A. Daniel; Lecomte, Juliette T. J.

doi:10.1021/ja026569c

Cited by 57 publications

(76 citation statements)

References 15 publications

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“…These oligo-binding proteins have a common function in binding and releasing non-protein molecules, which is consistent with the known functions of CcmE. Covalent heme attachment to a histidine side chain of a protein has been described for an algal Hb variant that contains a bis-His coordinated heme covalently bound to the protein through the N⑀2 of a histidine and the 2-vinyl group of the heme (10).…”

supporting

confidence: 69%

The Interaction of Covalently Bound Heme with the Cytochrome c Maturation Protein CcmE

Uchida

Stevens

Daltrop

et al. 2004

Journal of Biological Chemistry

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The heme chaperone CcmE is a novel protein that binds heme covalently via a histidine residue as part of its essential function in the process of cytochrome c biogenesis in many bacteria as well as plant mitochondria. In the continued absence of a structure of the holoform of CcmE, identification of the heme ligands is an important step in understanding the molecular function of this protein and the role of covalent heme binding to CcmE during the maturation of c-type cytochromes. In this work, we present spectroscopic data that provide insight into the ligation of the heme iron in the soluble domain of CcmE from Escherichia coli. Resonance Raman spectra demonstrated that one of the heme axial ligands is a histidine residue and that the other is likely to be Tyr 134 . In addition, the properties of the heme resonances of the holo-protein as compared with those of a form of CcmE with non-covalently bound heme provide evidence for the modification of one of the heme vinyl side chains by the protein, most likely the 2-vinyl group.

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supporting

confidence: 69%

The Interaction of Covalently Bound Heme with the Cytochrome c Maturation Protein CcmE

Uchida

Stevens

Daltrop

et al. 2004

Journal of Biological Chemistry

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“…Although the function of this covalent linkage is not yet understood, its structural implications are evident from a comparison of the crystal and NMR structures. Potential functional significance resulting from the covalent linkage includes inward movement of helices and heme pocket residues toward the heme resulting in decreased solvent accessibility and increased protein stability due to prevention of heme loss (27).…”

Section: Discussionmentioning

confidence: 99%

“…However, the reported method of dithionite treatment leading to the covalent link (27,28) was not used in our treatment of the protein. Crystal growth was achieved by hanging-drop vapor diffusion.…”

Section: Methodsmentioning

confidence: 99%

“…They are further characterized by a hydrophobic tunnel connecting the protein surface to the distal heme pocket that could serve as a direct route for ligand entry and/or exit from the heme pocket (2). In addition to being a hexacoordinate member of the trHb family, SynHb is distinguished by the ability to form a covalent bond between the heme 2-vinyl group and the His 117 side chain (27); this is a novel example of covalent attachment in a Hb via the porphyrin ring, and the purpose of this modification is not yet understood.…”

mentioning

confidence: 99%

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The Crystal Structure of Synechocystis Hemoglobin with a Covalent Heme Linkage

Hoy

Kundu

Trent

et al. 2004

Journal of Biological Chemistry

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The x-ray crystal structure of Synechocystis hemoglobin has been solved to a resolution of 1.8 Å. The conformation of this structure is surprisingly different from that of the previously reported solution structure, probably due in part to a covalent linkage between the heme 2-vinyl and His 117 that is present in the crystal structure but not in the structure solved by NMR. Synechocystis hemoglobin is a hexacoordinate hemoglobin in which the heme iron is coordinated by both the proximal and distal histidines. It is also a member of the "truncated hemoglobin" family that is much shorter in primary structure than vertebrate and plant hemoglobins. In contrast to other truncated hemoglobins, the crystal structure of Synechocystis hemoglobin displays no "ligand tunnel" and shows that several important amino acid side chains extrude into the solvent instead of residing inside the heme pocket. The stereochemistry of hexacoordination is compared with other hexacoordinate hemoglobins and cytochromes in an effort to illuminate factors contributing to ligand affinity in hexacoordinate hemoglobins.

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“…To examine the role of residue F7, a serine was introduced at this position. In vitro, S6803 rHb can attach the heme covalently through the formation of a bond between His117 and the heme 2-vinyl (40). In the absence of information on the physiologically relevant form(s) of the protein, we first focused on the protein in which this cross-link, extremely rare among Hbs, was not formed (rHb-R).…”

mentioning

confidence: 99%

Proximal Influences in Two-on-Two Globins: Effect of the Ala69Ser Replacement on Synechocystis sp. PCC 6803 Hemoglobin

Knappenberger

Kuriakose

et al. 2006

Biochemistry

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The cyanobacterium Synechocystis sp. PCC 6803 (S6803) expresses a two-on-two globin in which His46 (distal side) and His70 (proximal) function as heme iron axial ligands. His46 can be displaced by O 2 , CO, and CN − , among others, whereas His70 is not labile under native conditions. The residue preceding the proximal histidine has been implicated in controlling globin axial ligand reactivity; the details of the mechanism, however, are not well understood, and little information exists for bis-histidyl hexacoordinate proteins. In many vertebrate hemoglobins and in the Synechocystis protein, the position is occupied by an alanine whereas, in myoglobins, it is a serine involved in an intricate hydrogen bond network. We examined the role of Ala69 in S6803 hemoglobin through the effects of an Ala → Ser replacement. The substitution resulted in minor structural perturbations, but the holoprotein's response to temperature-, urea-, and acid-induced denaturation was measurably affected. Enhanced three-state behavior was manifested in the decoupling of heme binding and secondary structure formation. Urea-gradient gel experiments revealed that the stability of the apoprotein was unchanged by the replacement and that a slight alteration of the folding kinetics occurred in the holoproteins. Cyanide-binding experiments were performed to assess trans effects. The apparent rate constant for association decreased two-fold upon Ala69Ser replacement. This deceleration was attributed to a change in the lifetime of a state containing a decoordinated His46. The results demonstrated that, as in vertebrate globins and leghemoglobin, proximal influences operate to determine fundamental dynamic and thermodynamic properties of the protein.Keywords truncated hemoglobin; 2-on-2 globin; hexacoordinate hemoglobin; urea-gradient gel; heme binding; thermodynamic stabilityIron protoporphyrin IX (Fe-PPIX) 1 serves as a cofactor in a large number of essential proteins. In the absence of covalent attachment to the protein matrix via protoporphyrin substituents, the contact between Fe(II)-PPIX (or b heme) and the protein is limited to ligation bond(s) to the iron, hydrogen bonding, van der Waals and electrostatic interactions, and hydrophobic † This study was supported by National Science Foundation grants MCB-091182 and MCB-0349409, National Institutes of Health grant GM-054217, and NASA grant NNG04GN33H (DAV).* To whom correspondence should be addressed. Tel: (814) NIH Public Access Author ManuscriptBiochemistry. Author manuscript; available in PMC 2008 September 11. forces. The affinity for the heme group and its chemical properties, such as redox potential, ability to bind various ligands, and propensity for generating reactive oxygen species, are strictly controlled by the protein environment.In many b hemoproteins the iron is endogenously hexacoordinated, with the axial positions of its octahedral geometry filled by two histidine side chains (1). A well-known example is cytochrome b 5 , an electron-transfer protein that does not bind...

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Novel Histidine−Heme Covalent Linkage in a Hemoglobin

Cited by 57 publications

References 15 publications

The Interaction of Covalently Bound Heme with the Cytochrome c Maturation Protein CcmE

The Interaction of Covalently Bound Heme with the Cytochrome c Maturation Protein CcmE

The Crystal Structure of Synechocystis Hemoglobin with a Covalent Heme Linkage

Proximal Influences in Two-on-Two Globins: Effect of the Ala69Ser Replacement on Synechocystis sp. PCC 6803 Hemoglobin

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