NMR reveals hydrogen bonds between oxygen and distal histidines in oxyhemoglobin

Lukin, Jonathan A.; Simplăceanu, Virgil; Zou, Ming; Ho, Nancy T.; Ho, Chien

doi:10.1073/pnas.190254697

Cited by 73 publications

(70 citation statements)

References 44 publications

(55 reference statements)

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“…32,35,36,42 The vibrational echo measurements reported here confirm that H64 plays a significant role in dephasing of the CO vibration in myoglobin. Vibrational echo decays measured in H64V are considerably slower than those in wtMbCO.…”

Section: Discussionsupporting

confidence: 67%

“…5,8,10,11 A wealth of experimental and theoretical evidence underscores the importance of H64 in myoglobin function and dynamics. 23,[30][31][32][33] H64 is the most polar residue near the active site, and interacts strongly with both CO and O 2 ligands. H64 has been implicated in the physiologically important differentiation between CO and O 2 binding to the heme group of myoglobin and hemoglobin.…”

Section: Introductionmentioning

confidence: 99%

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Ultrafast Dynamics of Myoglobin without the Distal Histidine: Stimulated Vibrational Echo Experiments and Molecular Dynamics Simulations

et al. 2005

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Ultrafast protein dynamics of the CO adduct of a myoglobin mutant with the polar distal histidine replaced by a nonpolar valine (H64V) have been investigated by spectrally resolved infrared stimulated vibrational echo experiments and molecular dynamics (MD) simulations. In aqueous solution at room temperature, the vibrational dephasing rate of CO in the mutant is reduced by ∼50% relative to the native protein. This finding confirms that the dephasing of the CO vibration in the native protein is sensitive to the interaction between the ligand and the distal histidine. The stimulated vibrational echo observable is calculated from MD simulations of H64V within a model in which vibrational dephasing is driven by electrostatic forces. In agreement with experiment, calculated vibrational echoes show slower dephasing for the mutant than for the native protein. However, vibrational echoes calculated for H64V do not show the quantitative agreement with measurements demonstrated previously for the native protein.

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Section: Discussionsupporting

confidence: 67%

Section: Introductionmentioning

confidence: 99%

Ultrafast Dynamics of Myoglobin without the Distal Histidine: Stimulated Vibrational Echo Experiments and Molecular Dynamics Simulations

et al. 2005

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“…Bound O 2 is well known to experience a larger electrostatic attraction to the protein than bound CO does. Accounting for protein discrimination between the two ligands (28,29), it is plausible that a small ␣-␤ difference in electrostatic energy would appear with the substitution of O 2 for CO.…”

Section: Resultsmentioning

confidence: 99%

“…Protein Data Bank (PDB) structures 1A3N (deoxy, T state) and 1BBB (carbonmonoxy, R2 state) were protonated and missing residues were filled in with the PLOP code (42). Distal histidines were assumed to be protonated at the ⑀-position, in both T and R structures (28). The protonation state of the rest of the histidines was assessed by visual inspection.…”

Section: Methodsmentioning

confidence: 99%

A quantum-chemical picture of hemoglobin affinity

Alcantara

Spiro

et al. 2007

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

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Understanding the molecular mechanism of hemoglobin cooperativity remains an enduring challenge. Protein forces that control ligand affinity are not directly accessible by experiment. We demonstrate that computational quantum mechanics/molecular mechanics methods can provide reasonable values of ligand binding energies in Hb, and of their dependence on allostery. About 40% of the binding energy differences between the relaxed state and tense state quaternary structures result from strain induced in the heme and its ligands, especially in one of the pyrrole rings. The proximal histidine also contributes significantly, in particular, in the ␣-chains. The remaining energy difference resides in protein contacts, involving residues responsible for locking the quaternary changes. In the ␣-chains, the most important contacts involve the FG corner, at the ''hinge'' region of the ␣1␤2 quaternary interface. The energy differences are spread more evenly among the ␤-chain residues, suggesting greater flexibility for the ␤-than for the ␣-chains along the quaternary transition. Despite this chain differentiation, the chains contribute equally to the relaxed substitute state energy difference. Thus, nature has evolved a symmetric response to the quaternary structure change, which is a requirement for maximum cooperativity, via different mechanisms for the two kinds of chains.allostery ͉ cooperativity ͉ heme ͉ quantum mechanics/molecular mechanics H emoglobin has been a paradigm for our understanding of multisubunit proteins, beginning with the pioneering work of Adair (1) and then with the elucidation of the oxygenated and deoxygenated crystal structures of Hb by Perutz (2), some four decades ago. Interest in Hb continues to the present, with new experimental and theoretical methods aimed at characterizing intermediate ligation states of the molecule (3-5) and at gaining a deeper understanding of its allosteric transition (6-11).The Hb molecule is composed of four chains that contain a heme group capable of reversibly binding CO or O 2 . The molecule is arranged as a dimer of dimers, where each dimer is made up of an ␣-and a ␤-chain (denoted as ␣ 1 ␤ 1 or ␣ 2 ␤ 2 ) with a hydrophobic intradimer interface. Adair observed that Hb binds oxygen in a cooperative manner, successive ligation events occurring with higher affinity. For some time it was believed that such cooperativity could be explained by direct interaction of the closely packed heme groups. However the 1960s saw the appearance of the first allosteric models for Hb cooperativity. In particular, the Monod-Wyman-Changeux (12) model postulated the existence of two states of the molecule: the relaxed (R) state with high ligand affinity and the tense (T) state with low affinity. Ligand binding preferentially stabilized the R form and led to cooperativity. Early Hb crystallization attempts revealed that deoxy crystals would shatter when exposed to oxygen, which suggested that a quaternary rearrangement was associated with the T-R transition of the molecule.Crystal structure...

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“…In 2000, Ho and co-workers (25) used heteronuclear NMR spectra of chain-selectively labeled samples to show that the N⑀ and not the N␦ atoms of the His(E7) imidazole rings are protonated and capable of donating hydrogen bonds to bound O 2 in both the ␣ and ␤ subunits of HbO 2 . In 2006, Tame and coworkers (26) reported a new high resolution crystal structure (1.25 Å) of HbAO 2 .…”

mentioning

confidence: 99%

Distal Histidine Stabilizes Bound O2 and Acts as a Gate for Ligand Entry in Both Subunits of Adult Human Hemoglobin

Birukou

Schweers²,

Olson

2010

Journal of Biological Chemistry

100

174

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The role of the distal histidine in regulating ligand binding to adult human hemoglobin (HbA) was re-examined systematically by preparing His(E7) to Gly, Ala, Leu, Gln, Phe, and Trp mutants of both Hb subunits. Rate constants for O 2 , CO, and NO binding were measured using rapid mixing and laser photolysis experiments designed to minimize autoxidation of the unstable apolar E7 mutants. Replacing His(E7) with Gly, Ala, Leu, or Phe causes 20 -500-fold increases in the rates of O 2 dissociation from either Hb subunit, demonstrating unambiguously that the native His(E7) imidazole side chain forms a strong hydrogen bond with bound O 2 in both the ␣ and ␤ chains (⌬G His(E7)H-bond ≈ ؊8 kJ/mol). As the size of the E7 amino acid is increased from Gly to Phe, decreases in k O2 , In 1970, Perutz (1) proposed that the distal histidines located at the E7 helical positions, 3 ␣His-58 and ␤His-63, play crucial structural roles for regulating both the affinities and rates of O 2 binding to adult human hemoglobin (HbA). 4 These ideas were based on the suggestion by Pauling (2) that His(E7) could stabilize bound O 2 by donating a hydrogen bond to the partial negative charge on the superoxide-Fe(III)-like FeO 2 complex and on the idea by Perutz and Mathews (3) that the distal histidine could also be acting as gate for ligand entry and exit. Studies of model heme compounds and naturally occurring globins with His(E7) replacements suggested strongly that the distal histidine also plays a key role in discrimination between O 2 and CO binding (4 -9).The first mutagenesis studies on sperm whale Mb and human HbA reported that His(E7) to Gly mutations in ␣ subunits and Mb cause marked increases in the rates of O 2 dissociation and significant decreases in affinity, both of which indicate strong stabilization of the FeO 2 complex by proton donation from the wild-type His(E7) side chain (7, 10, 11). In addition, the association rate constants for O 2 and CO binding increased 5-10-fold. The latter results were interpreted in terms of the distal histidine gate mechanism, with the His(E7) to Gly mutation resulting in an open E7 channel. In contrast, neither the dissociation nor association rate constants for O 2 binding to the R state ␤Gly(E7) mutant of HbA appeared to increase significantly, implying no electrostatic stabilization of bound ligands by the native His(E7) in ␤ subunits and an already open gate or alternative pathway. These surprising kinetic results were explained by the first high resolution structure of human oxyhemoglobin published by Shaanan (12), in which the N⑀H atoms of distal histidine in ␤ subunits seemed to be further away from the bound O 2 atoms and pointing toward the heme plane.Between 1989 and 1999, our group and others constructed large libraries of mammalian Mb mutants as a model system for understanding the structural mechanisms of ligand binding to vertebrate globins involved in O 2 transport and storage. A detailed molecular mechanism for O 2 binding has emerged. Ligand entry into myoglobin occurs through t...

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NMR reveals hydrogen bonds between oxygen and distal histidines in oxyhemoglobin

Cited by 73 publications

References 44 publications

Ultrafast Dynamics of Myoglobin without the Distal Histidine: Stimulated Vibrational Echo Experiments and Molecular Dynamics Simulations

Ultrafast Dynamics of Myoglobin without the Distal Histidine: Stimulated Vibrational Echo Experiments and Molecular Dynamics Simulations

A quantum-chemical picture of hemoglobin affinity

Distal Histidine Stabilizes Bound O2 and Acts as a Gate for Ligand Entry in Both Subunits of Adult Human Hemoglobin

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