Proton nuclear magnetic resonance study of histidine ionizations in myoglobins of various species. Specific assignment of individual resonances

Botelho, L; Gurd, Frank R. N.

doi:10.1021/bi00617a019

Cited by 48 publications

(17 citation statements)

References 58 publications

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“…The pK value for His-48 has been measured and predicted by several groups (26)(27)(28). Our result, along with results from these groups, is listed in Table 1.…”

Section: Resultssupporting

confidence: 56%

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Enhanced visibility of hydrogen atoms by neutron crystallography on fully deuterated myoglobin

Shu

Ramakrishnan

Schoenborn

2000

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

116

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Although hydrogens comprise half of the atoms in a protein molecule and are of great importance chemically and structurally, direct visualization of them by using crystallography is difficult. Neutron crystallography is capable of directly revealing the position of hydrogens, but its use on unlabeled samples faces certain technical difficulties: the large incoherent scattering of hydrogen results in background scattering that greatly reduces the signal to noise of the experiment. Moreover, whereas the scattering lengths of C, N, and O are positive, that of hydrogen is negative and about half the magnitude. This results in density for hydrogens being half as strong and close to the threshold of detection at 2.0-Å resolution. Also, because of its opposite sign, there is a partial cancellation of the hydrogen density with that from neighboring atoms, which can lead to ambiguities in interpretation at medium resolution. These difficulties can be overcome by the use of deuterated protein, and we present here a neutron structure of fully deuterated myoglobin. The structure reveals a wealth of chemical information about the molecule, including the geometry of hydrogen bonding, states of protonation of histidines, and the location and geometry of water molecules at the surface of the protein. The structure also should be of broader interest because it will serve as a benchmark for molecular dynamics and energy minimization calculations and for comparison with NMR studies.

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“…The pK value for His-48 has been measured and predicted by several groups (26)(27)(28). Our result, along with results from these groups, is listed in Table 1.…”

Section: Resultssupporting

confidence: 56%

“…They not only are related to the function of the protein, but also serve as a basis to model electrostatic interactions in proteins (26)(27)(28)(29)(30). Neutron crystallography can directly determine the protonation states of specific histidines (5,19).…”

Section: Discussionmentioning

confidence: 99%

Enhanced visibility of hydrogen atoms by neutron crystallography on fully deuterated myoglobin

Shu

Ramakrishnan

Schoenborn

2000

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

116

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“…The negative charge of CM‐Mb is due to addition of negative CH 2 COO – groups to His residues. All solvent‐accessible histidines can react with bromoacetate, His12, 13, 116 and 81, forming predominantly disubstituted derivatives that cannot be protonated in the pH 5–8 range, whereas His48 and 119 monoalkylated compounds are capable of accepting protons [11,12]. The absorption and CD spectra in the UV and visible regions, as well as the thermal stability of CM‐Mb and intact Mb, do not differ.…”

Section: Resultsmentioning

confidence: 99%

Ferrocyanide − a novel catalyst for oxymyoglobin oxidation by molecular oxygen

et al. 2007

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A comparative study of the rates of ferrocyanide‐catalyzed oxidation of several oxymyoglobins by molecular oxygen is reported. Oxidation of the native oxymyoglobins from sperm whale, horse and pig, as well as the chemically modified (MbO2) sperm whale oxymyoglobin, with all accessible His residues alkylated by sodium bromoacetate (CM‐MbO2), and the mutant sperm whale oxymyoglobin [MbO2(His119→Asp)], was studied. The effect of pH, ionic strength and the concentration of anionic catalyst ferrocyanide, [Fe(CN)6]4–, on the oxidation rate is investigated, as well as the effect of MbO2 complexing with redox‐inactive Zn2+, which forms the stable chelate complex with functional groups of His119, Lys16 and Asp122, all located nearby. The catalytic mechanism was demonstrated to involve specific [Fe(CN)6]4– binding to the protein in the His119 region, which agrees with a high local positive electrostatic potential and the presence of a cavity large enough to accommodate [Fe(CN)6]4– in that region. The protonation of the nearby His113 and especially His116 plays a very important role in the catalysis, accelerating the oxidation rate of bound [Fe(CN)6]4– by dissolved oxygen. The simultaneous occurrence of both these factors (i.e. specific binding of [Fe(CN)6]4– to the protein and its fast reoxidation by oxygen) is necessary for the efficient ferrocyanide‐catalyzed oxidation of oxymyoglobin.

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“…The results of Wilbur & Allerhand (1977) for the pK values of the other five histidine residues fit those of Tables I and II of Carver & Bradbury (1984). The postulated high pK of 5.6 for Glu-38 in metMb and CNMb may be due to the nonpolar nature and consequent inaccessibility of the region to solvent as shown by the slow rate of deuteration at pH 7 of His-36 H-2 (Botelho & Gurd, 1978).…”

Section: Resultsmentioning

confidence: 99%

Conformational differences between various myoglobin ligated states as monitored by proton NMR spectroscopy

Bradbury¹,

Carver²

1984

Biochemistry

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In paramagnetic metmyoglobin, cyanomyoglobin (CNMb), and deoxymyoglobin, His-36 has a high pK (approximately 8), and the NMR titration behavior of the H-2 resonance is perturbed, due to the presence at low pH of a hydrogen bond with Glu-38, which is broken at high pH. The His-36 H-4 resonance shows no shift with pK approximately 8 because of two opposing chemical shift effects but monitors the titration of nearby Glu-36 (pK = 5.6). In diamagnetic derivatives [(carbon monoxy)myoglobin (COMb) and oxymyoglobin (oxyMb)], the titration behavior of His-36 H-2 and H-4 resonances is normalized (pK approximately 6.8). The very slight alkaline Bohr effect in sperm whale myoglobin (Mb) is interpreted in terms of the pK change of His-36 from deoxyMb to oxyMb and compensating pK changes in the opposite direction of other unspecified groups. In sperm whale COMb at 40 degrees C, the distal histidine (His-64) and His-97 have pK values of 5.0 and 5.9. The meso proton resonances remote from these groups do not show a titration shift, but the nearby gamma-meso proton (pK = 5.3) responds to titration of both histidines, and the upfield Val-68 methyl at -2.3 ppm (pK = 4.7) witnesses the titration of nearby His-64. At 20 degrees C, the latter resonance is reduced in size, and a second resonance occurs at -2.8 ppm, which is insensitive to pH and, hence, more remote from His-64. Both resonances arise from two conformations of Val-68 in slow equilibrium. In oxyMb at 20 degrees C, only the latter resonance is observed, presumably because of the steric restrictions imposed by the hydrogen bond between ligand and His-64 in oxyMb, which is not present in COMb. In oxyMb the pK of His-97 (5.6) is similar to that of the meso proton resonances (5.5) and to the pK of other pH-dependent processes, including the very small acid Bohr effect. It is likely that these processes are controlled by the titration of His-97.(ABSTRACT TRUNCATED AT 250 WORDS)

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Proton nuclear magnetic resonance study of histidine ionizations in myoglobins of various species. Specific assignment of individual resonances

Cited by 48 publications

References 58 publications

Enhanced visibility of hydrogen atoms by neutron crystallography on fully deuterated myoglobin

Enhanced visibility of hydrogen atoms by neutron crystallography on fully deuterated myoglobin

Ferrocyanide − a novel catalyst for oxymyoglobin oxidation by molecular oxygen

Conformational differences between various myoglobin ligated states as monitored by proton NMR spectroscopy

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