Structure of cyanide methemoglobin

Deatherage, James F.; Loe, Richard S.; Anderson, Charles M.; Moffat, Keith

doi:10.1016/0022-2836(76)90129-7

Cited by 103 publications

(35 citation statements)

References 26 publications

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“…We have used cyanomet ligation as a probe of this control system. While we do not assume the effects of cyanomet ligation to be quantitatively the same as those of oxygenation, there are strong reasons to believe that the basic modes of free energy coupling within the hemoglobin tetramer will be the same when heme sites are perturbed with different ligands: (i) The crystallographic structures of cyanomet (horse) hemoglobin (19), human -IProc. Natl.…”

Section: Discussionmentioning

confidence: 99%

Experimental resolution of cooperative free energies for the ten ligation states of human hemoglobin.

Smith¹,

Ackers²

1985

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

101

123

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Tetrameric human hemoglobin can assume ten molecular forms that differ in the number and configuration of ligands bound at the four heme sites. For each of these species we have determined the cooperative free energy-i.e., the deviation in free energy of ligation from that which would obtain for the same sites binding as independent a and f8 subunits. These cooperative free energies were resolved from measurements on the dissociation into dimers of tetramers in which each subunit is either unligated (Fe2' deoxy) or "ligated" by conversion into the cyanomet form (Fe31 CN). The results indicate that each hemoglobin tetramer acts as a three-level molecular switch. During the course of ligation, the total cooperative free energy (6 kcal/mol over all four binding steps) is expended in two transitions that are synchronized with particular ligation steps. Whether a cooperative energy transition occurs or not depends upon how the ligation step changes both the number and configuration of ligated subunits. The hemoglobin tetramer is thus a "combinatorial switch." The finding of three distinct free energy levels for the ten ligation states suggests the existence of three major structural forms of the hemoglobin tetramer.

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Section: Discussionmentioning

confidence: 99%

Experimental resolution of cooperative free energies for the ten ligation states of human hemoglobin.

Smith¹,

Ackers²

1985

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

101

123

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“…The heme in a protein binds to a cyanide with the C-N bond being often tilted from the normal of the heme plane, where two ways of binding are possible: tilt and bent conformations (Deatherage et al, 1976). As deviation from the spherical shape of the electron density is small due to the short C-N distance of the cyanide (1.15 Å), it was difficult to define its orientation precisely even by 1.6-Å resolution analysis.…”

Section: Formation Of the Complexes-mentioning

confidence: 99%

Crystal Structures of Cyanide- and Triiodide-bound Forms of Arthromyces ramosus Peroxidase at Different pH Values

Fukuyama

Kunishima

Amada

et al. 1995

Journal of Biological Chemistry

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The structures of the cyanide and triiodide complexes of Arthromyces ramosus peroxidase (ARP) at different pH values were investigated by x-ray crystallography in order to examine the behavior of the invariant residues of arginine (Arg-52) and distal histidine (His-56) during the enzyme reaction as well as to provide the structural basis of the active site of peroxidase. The models of the cyanide complexes at pH 7.5, 5.0, and 4.0, respectively, were refined to the R-factors of 17.8, 17.8, and 18.5% using 7.0 -1.6-Å resolution data, and those of the triiodide complexes at pH 6.5 and 5.0 refined to 16.9 and 16.8% using 7.0 -1.9-Å resolution data.The structures of the cyanide complexes at pH 7.5, 5.0, and 4.0 are identical within experimental error. Cyanide ion bound to the heme in the bent conformation rather than in the tilt conformation. Upon cyanide ion binding, the N ⑀ atom of His-56 moved toward the ion by rotation of the imidazole ring around the C ␤ -C ␥ bond, but there was little conformational change in the remaining residues. The distance between the N ⑀ atom of His-56 and the nitrogen atom of the cyanide suggests the presence of a hydrogen bond between them in the pH range investigated. In the triiodide complexes, one of the two triiodides bound to ARP was located at the distal side of the heme. When triiodide bound to ARP, unlike the rearrangement of the distal arginine of cytochrome c peroxidase that occurs on formation of the fluoride complex or compound I, the side chain of Arg-52 moved little. The conformation of the side chain of His-56, however, changed markedly. Conformational flexibility of His-56 appears to be a requisite for proton translocation from one oxygen atom to the other of HOO ؊ by acid-base catalysis to produce compound I. The iron atom in each cyanide complex (low-spin ferric) is located in the heme plane, whereas in each triiodide complex (high-spin ferric) the iron atom is displaced from the plane about 0.2 Å toward the proximal side.

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“…The validity of this mechanism in the meso-hydroxylation of heme in oxyhemoproteins is supported by the hydroxylation of specific meso positions in myoglobin and hemoglobin. Ligands are directed toward the a methene bridge in myoglobin and toward pyrrole II (situated between the a and p bridges) in hemoglobin (37)(38)(39). The a methene bridge in myoglobin and the a and ,B bridges in hemoglobin are the only bridges hydroxylated when these proteins undergo coupled oxidation with ascorbate (40).…”

Section: Discussionmentioning

confidence: 99%

Ligands and oxidants in ferrihemochrome formation and oxidative hemolysis

Itano

Hirota

Vedvick

1977

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

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We have investigated the effect of size of a single neutral ring substituent on the induction of hemolytic anemia and the formation of a ferrihemochrome by substituted phenylhydrazines. The severity of induced anemia decreased with increase in size of a halogen atom or an alkyl group ortho to the hydrazino group, little anemia resulting from 2-iodophenylhydrazine and no anemia from 2-tert-butylphenylhydrazine. The size of a halogen atom or an alkyl group at the meta or para position had relatively little effect on the severity of induced anemia. The ability of an arylhydrazine to induce hemolytic anemia paralleled its ability to produce a ferrihemochrome with an exogenous ligand, probably the corresponding aryldiazene. In general, rapid and complete formation of ferrihemochrome occurred-with arylhydrazines that induced severe anemia. The degree of hemolysis induced by an arylhydrazine was not related to its rate of autooxidation, i.e., the rate at which oxidants are formed by the reduction of oxygen. We propose a mechanism of arylhydrazine-induced oxidative denaturation based on the simultaneous formation of hydroxyl radical and aryldiazene ferrihemochrome in a reaction of oxyhemoglobin with arylhydrazine. We suggest that after oxidation of the porphyrin ring is initiated by a hydroxyl radical, oxidative cleavage of the ring is facilitated by the presence of a large li-

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Structure of cyanide methemoglobin

Cited by 103 publications

References 26 publications

Experimental resolution of cooperative free energies for the ten ligation states of human hemoglobin.

Experimental resolution of cooperative free energies for the ten ligation states of human hemoglobin.

Crystal Structures of Cyanide- and Triiodide-bound Forms of Arthromyces ramosus Peroxidase at Different pH Values

Ligands and oxidants in ferrihemochrome formation and oxidative hemolysis

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