Solution NMR Determination of the Anisotropy and Orientation of the Paramagnetic Susceptibility Tensor as a Function of Temperature for Metmyoglobin Cyanide:  Implications for the Population of Excited Electronic States

Nguyen, Bao D.; Xia, Zhicheng; Yeh, Deok Cheon; Vyas, K.; Deaguero, and Helen; Mar, Gerd N. La

doi:10.1021/ja982555o

Cited by 39 publications

(101 citation statements)

References 45 publications

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“…Lastly, the magnetic axes reported above allow the determination of ␦ dip for the axial His, which, in turn, provides ␦ con for each of the positions, as shown in Table I. Thus only the C ⑀ H exhibits large contact shifts that are very similar to those reported for sperm whale metMbCN (70) and confirms an essentially conserved axial His-Fe bond in A. suum relative to sperm whale Mb.…”

Section: Discussionsupporting

confidence: 56%

1H NMR Investigation of the Distal Hydrogen Bonding Network and Ligand Tilt in the Cyanomet Complex of Oxygen-avidAscaris suum Hemoglobin

Xia

Zhang

Nguyen

et al. 1999

Journal of Biological Chemistry

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The O 2 -avid hemoglobin from the parasitic nematode Ascaris suum exhibits one of the slowest known O 2 off rates. Solution 1 H NMR has been used to investigate the electronic and molecular structural properties of the active site for the cyano-met derivative of the recombinant first domain of this protein. Assignment of the heme, axial His, and majority of the residues in contact with the heme reveals a molecular structure that is the same as reported in the A. suum HbO 2 crystal structure (Yang, J., Kloek, A., Goldberg, D. E., and Mathews, F. S. (1995) Proc. Natl. Acad. Sci. U. S. A. 92, 4224 -4228) with the exception that the heme in solution is rotated by 180°about the ␣,␥-meso axis relative to that in the crystal. The observed dipolar shifts, together with the crystal coordinates of HbO 2 , provide the orientation of the magnetic axes in the molecular framework. The major magnetic axis, which correlates with the Fe-CN vector, is found oriented ϳ30°away from the heme normal and indicates significant steric tilt because of interaction with Tyr 30 (B10). The three side chain labile protons for the distal residues Tyr 30 (B10) and Gln 64 (E7) were identified, and their relaxation, dipolar shifts, and nuclear Overhauser effects to adjacent residues used to place them in the distal pocket. It is shown that these two distal residues exhibit the same orientations ideal for H bonding to the ligand and to each other, as found in the A. suum HbO 2 crystal. It is concluded that the ligated cyanide participates in the same distal H bonding network as ligated O 2 . The combination of the strong steric tilt of the bound cyanide and slow ring reorientation of the Tyr 30 (B10) side chain supports a crowded and constrained distal pocket.The O 2 binding globins, myoglobin (Mb) 1 and hemoglobin (Hb), despite highly varied sequences throughout phylogeny, possess a highly conserved folding topology of 7-8 helices (A-H), with the heme wedged in between the E and F helices and ligated by one, His F8 (proximal), of only two (the other is Phe CD1) completely conserved residues (1-3). Despite this strong structural homology, the O 2 ligation rates and O 2 affinities vary over a remarkably wide range (by ϳ10 5 ), depending on the exact nature of several distal residues at the key positions B10, E7, and E10 (4 -8). The most important distal interaction for stabilizing bound O 2 is hydrogen bonding to the ligand, for which the donor is generally His E7 (1, 7, 9, 10) and is Gln E7 in a few cases (2). In several invertebrates, such as Aplysia and Dolbella Mbs that possess a Val E7, the distal H bond to the ligand is provided by an Arg at position E10 (11-13).A particularly noteworthy class of globins is that of parasitic nematodes that possess, in addition to a H bond donor at position E7, a Tyr at position B10 that is also capable of H bonding to the ligand (4, 5, 8, 14 -17 (5,15). The positions of these two key residues are clearly defined in the crystal structure of A. suum HbO 2 , in which the two residues are appropriately poised ...

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Section: Discussionsupporting

confidence: 56%

1H NMR Investigation of the Distal Hydrogen Bonding Network and Ligand Tilt in the Cyanomet Complex of Oxygen-avidAscaris suum Hemoglobin

Xia

Zhang

Nguyen

et al. 1999

Journal of Biological Chemistry

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“…1). The values of obtained from the magnetic axes, however, have Ϯ10°uncer-tainties (35) and indicate that for the four complexes of interest is the same within the uncertainties. Nevertheless, changes in and manifest themselves in extraordinarily sensitive manners in the heme hyperfine shift patterns (30 -34).…”

Section: H Nmr Chemical Shifts For Heme and Axial His Resonances Of Amentioning

confidence: 78%

“…1) (29 -33), and the pattern of the dominant meso-H dipolar shift reflects the orientation of the rhombic magnetic axes ( in Fig. 1) (34,35). The mean of the heme methyl contact shifts has been shown to be sensitive to distal H-bonding to bound cyanide in models (36), but it has not yet been assessed in globins.…”

Section: Myoglobin (Mb)mentioning

confidence: 99%

Solution 1H NMR Study of the Influence of Distal Hydrogen Bonding and N Terminus Acetylation on the Active Site Electronic and Molecular Structure of Aplysia limacinaCyanomet Myoglobin

Nguyen¹,

Xia²,

Cutruzzolà³

et al. 2000

Journal of Biological Chemistry

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The sea hare Aplysia limacina possesses a myoglobin in which a distal H-bond is provided by Arg E10 rather than the common His E7. Solution 1 H NMR studies of the cyanomet complexes of true wild-type (WT), recombinant wild-type (rWT), and the V(E7)H/R(E10)T and V(E7)H mutants of Aplysia Mb designed to mimic the mammalian Mb heme pocket reveal that the distal His in the mutants is rotated out of the heme pocket and is unable to provide a stabilizing H-bond to bound ligand and that WT and rWT differ both in the thermodynamics of heme orientational disorder and in heme contact shift pattern. The mean of the four heme methyl shifts is shown to serve as a sensitive indicator of variations in distal H-bonding among a set of mutant cyanomet globins. The heme pocket perturbations in rWT relative to WT were traced to the absence of the N-terminal acetyl group in rWT that participates in an H-bond to the EF corner in WT. Analysis of dipolar contacts between heme and axial His and between heme and the protein matrix reveal a small ϳ2°rotation of the axial His in rWT relative to true WT and a ϳ3°rotation of the heme in the double mutant relative to rWT Mb. It is demonstrated that both the direction and magnitude of the rotation of the axial His relative to the heme can be determined from the change in the pattern of the contact-dominated heme methyl shift and from the dipolar-dominated heme meso-H shift. However, only NOE data can determine whether it is the His or heme that actually rotates in the protein matrix. Myoglobin (Mb)1 is a member of the globin family of proteins of approximately 140 -150 residues that encapsulate heme and exhibit a remarkably strongly conserved fold of seven to eight helices (A-H) despite a high variability in sequence (1-3). The heme is wedged between the E and F helices, and only the axial (proximal) His F8 (eighth residue on helix F) and Phe CD1 (first residue on the loop between the C and D helices) are completely conserved. This conserved globin fold, however, results in a very wide range of functionality, which appears to be controlled primarily by the nature of the "distal" residues at position E7, E11, E10, and B10 that line the ligand binding pocket (4). The major interaction that strongly stabilizes O 2 over CO binding has been shown to involve H-bonding to the bound O 2 by a distal residue, although destabilization of the bound CO by distal steric interaction cannot be completely discounted (4 -6). Although the distal H-bond in vertebrate globins is always provided by residue E7 (which is overwhelmingly His, but occasionally Gln (2)), there is much more variation in the nature of the E7 residue and the position of the distal H-bond donor in nonvertebrate globins (3). Such alternate residue H-bond stabilization of the bound O 2 has been established in natural globins from sea hares (Arg E10) (7) and trematodes (Tyr B10) (8 -10) and in synthetic globins at position E11 (Asn and Thr) (11).An effective strategy for determining the role of individual residues is to perform functional and m...

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“…A strongly relaxed labile proton was observed at 16.2 ppm that, with a T 1 * 15 ms, had to arise from a proton as distal residue *4Å from the iron. Detailed assignments and magnetic axes determination revealed (13) unchanged Dws, relative to sperm whale metMbCN (11), with a ¼ 368 + 68, and b ¼ 118, and an excellent correlation between d dip (calc) and d dip (calc) for all but the Arg(E10) residue, as shown in Figure 6A. Figure 6B, which clearly show (13) that the Arg(E10) terminus is in the heme pocket, like in metMbF (þsigns), and not out like in metMbH 2 O (closed triangles).…”

Section: Globinsmentioning

confidence: 98%

Application of the paramagnetic dipole field for solution NMR active site structure determination in low‐spin, cyanide‐inhibited ferric hemoproteins

Mar¹

2007

IUBMB Life

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SummaryThe principles for the application of the paramagnetic dipolar field of low-spin, cyanide-inhibited ferrihemoproteins for determining active site structure are briefly described. The ubiquitous dipolar shifts for assigned residues, together with crystal coordinates of some appropriate structural homolog, allow determination of the orientation and anisotropies of the paramagnetic dipolar tensor. The orientation of w uniquely defines the orientation of the Fe-CN unit, which is tilted variably and sensitively monitors distal steric and H-bond interactions. The mapped dipolar field, in turn, can be used to determine the orientation of mutated residues. Case studies involving unusual genetic variants and point mutants of myoglobins, human hemoglobins, horseradish peroxidase and its substrate complex of heme oxygenase are presented as examples.IUBMB Life, 59: 513-527, 2007

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Solution NMR Determination of the Anisotropy and Orientation of the Paramagnetic Susceptibility Tensor as a Function of Temperature for Metmyoglobin Cyanide: Implications for the Population of Excited Electronic States

Cited by 39 publications

References 45 publications

1H NMR Investigation of the Distal Hydrogen Bonding Network and Ligand Tilt in the Cyanomet Complex of Oxygen-avidAscaris suum Hemoglobin

1H NMR Investigation of the Distal Hydrogen Bonding Network and Ligand Tilt in the Cyanomet Complex of Oxygen-avidAscaris suum Hemoglobin

Solution 1H NMR Study of the Influence of Distal Hydrogen Bonding and N Terminus Acetylation on the Active Site Electronic and Molecular Structure of Aplysia limacinaCyanomet Myoglobin

Application of the paramagnetic dipole field for solution NMR active site structure determination in low‐spin, cyanide‐inhibited ferric hemoproteins

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