A proton magnetic resonance study of the distal histidine of soybean Leghemoglobin. Effects of nicotinate and other heme ligands.

Johnson, Robert N.; Bradbury, J. H.; Appleby, Cyril A.

doi:10.1016/s0021-9258(17)38052-3

Cited by 39 publications

(14 citation statements)

References 28 publications

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“…The pXa value (5.8) obtained for resonance H-9 is consistent with the value (5.6) attributed to His-64 by Hayashi et al (1976), determined spectrophotometrically, and by Saito et al (1977), by electron spin resonance of oxy-CoMb (5.5), but is lower than the value (7.8) calculated by Shire et al (1975). A pXa value of 6.0 has also recently been reported for the distal histidine residue of the heterologous soybean leghemoglobin (Johnson et al, 1978).…”

Section: Resultssupporting

confidence: 91%

NMR titration curves of histidine ring protons. 11. Near-heme histidine residues of deoxy- and oxymyoglobins

Ohms¹,

Hagenmaier²,

Hayes³

et al. 1979

Biochemistry

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Proton NMR titration curves of the histidine Cepsilon-H resonances of the deoxy and oxy forms of human, horse, and sperm whale myoglobins (Mb) were determined and compared with the results for the met and azide forms. One extra titrating resonance (H-8) was observed for each deoxy-Mb compared with the corresponding met-Mb, and a further extra resonance (H-9) was observed for the oxy-Mb form. These resonances correspond to the two additional resonances previously described for azide-Mb [Hayes, M., Hagenmaier, H., & Cohen, J. S. (1975) J. Biol. Chem. 250, 7461--7472]. This new evidence prompts us to reassign these resonances to the near-heme histidine residues.

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Section: Resultssupporting

confidence: 91%

NMR titration curves of histidine ring protons. 11. Near-heme histidine residues of deoxy- and oxymyoglobins

Ohms¹,

Hagenmaier²,

Hayes³

et al. 1979

Biochemistry

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“…We note that proton magnetic resonance studies of the distal histidine in leghemoglobin strongly support the above view (Johnson et al, 1978). Although holding to a two-level Henderson-Hasselbalch analysis for the titration data, two separate pATs are observed for the pyridine (pAf = 6.0) and CO (pK = 4.0) complexes.…”

Section: Resultssupporting

confidence: 59%

“…The 0/ population ratio is affected by pH in native Mb, but not in the MbGly or MbMet mutants. This fact is strong evidence in favor of the view (Hayashi et al, 1976;Johnson et al, 1978;Fuchsman & Appleby, 1979;Satterlee, 1984) that distal histidine-E7 contains a titratable proton that somehow affects the CO binding through geometry and/or polarization effects. It is important to note, however, that the mutants do show distinct evidence for the presence of both the A0 and states (Figure 4), although in differing proportions.…”

Section: Resultsmentioning

confidence: 96%

“…We have noticed that a number of studies involving pH titration in the Mb system have employed the simple two-state Henderson-Haselbalch analysis (Shimada & Caughey, 1982;Fuchsman & Appleby, 1979;Hayashi et al, 1976;Johnson et al, 1978;Doster et al, 1982;Coletta et al, 1985). In such an analysis, the two states that are assumed accessible to the system are defined by acidic and basic "limits" of the observed quantity that presume 100% population of the two states at the pH extremes.…”

Section: Resultsmentioning

confidence: 99%

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Resonance Raman investigations of site-directed mutants of myoglobin: effects of distal histidine replacement

et al. 1989

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The resonance Raman spectra of met-, deoxy-, and (carbonmonoxy)myoglobin (MbCO) are studied as a function of amino acid replacement at the distal histidine-E7 position. The synthetic wild type is found to be spectroscopically identical with the native material. The methionine and glycine replacements do not affect the met or deoxy spectra but do lead to distinct changes in the nu Fe-CO region of the MbCO spectrum. The native MbCO displays a pH-dependent population redistribution of the nu Fe-CO modes, while the analogous population in the mutant systems is found to be pH independent. This indicates that histidine-E7 is the titratable group in native MbCO. Moreover, the pH dependence of the population dynamics is found to be inconsistent with a simple two-state Henderson-Hasselbalch analysis. Instead, we suggest a four-state model involving the coupling of histidine protonation and conformational change. Within this model, the pK of the distal histidine is found to be 6.0 in the "open" configuration and 3.8 in the "closed" conformation. This corresponds to a 3 kcal/mol destabilization of the positively charged distal histidine within the hydrophobic pocket and suggests how protonation can lead to a larger population of the "open" conformation. At pH 7, the pocket is found to be "open" approximately 3% of the time. Further work, involving both IR and Raman measurements, allows the electron-nuclear coupling strengths of the various nu Fe-CO and nu C-O Raman modes to be determined. The slowly rebinding conformational state, corresponding to nu Fe-CO = 518 cm-1 (nu C-O = 1932 cm-1), displays unusually weak coupling of the Fe-CO mode to the Soret transition. Studies of the nu Fe-CO region as a function of temperature reveal that the equilibria between the conformational states are quenched in both the native and glycine mutant below the freezing point of the solvent. Unusual line narrowing of the nu Fe-CO modes at the phase transition is also observed in all samples studied. This line narrowing stands in marked contrast to the other heme Raman modes and suggests that Fe-CO librational motion and/or distal pocket vibrational (or conformational) excitations are involved in the line broadening at room temperature.

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“…The distal group has been suggested to be a histidine residue (Ikeda-Saito & Prince, 1985). Although the value of 4 is relatively low for a pKa value of the imidazole group of a histidine residue, such a pKa has been reported for the imidazole group of the distal histidine residue in leghemoglobin a (Johnson et al, 1978;Fuchsman & Appleby, 1979). The nature of the putative distal group in myeloperoxidase may be further explored by the aid of the thermodynamic parameters of its ionization.…”

Section: Discussionmentioning

confidence: 99%

A study of ligand binding to spleen myeloperoxidase

Ikeda‐Saito

1987

Biochemistry

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The ligand binding properties of spleen myeloperoxidase, a peroxidase formerly called "the spleen green hemeprotein", were studied as functions of temperature and pH, using chloride and cyanide as exogenous ligands. Ligand binding is influenced by a proton dissociable group with a pKa of 4. The protonated, uncharged form of cyanide binds to the unprotonated form of the enzyme, while chloride ion binds to the enzyme when this group is protonated. In both cyanide and chloride binding, the pH-dependent change in the apparent ligand affinity is due to a change in the apparent association rate with pH. The proton dissociable group on the enzyme involved in ligand binding has a delta H value of about 8 kcal . mol-1. The present results suggest that this ionizable group is the imidazole group of a histidine residue located near the ligand binding site.

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A proton magnetic resonance study of the distal histidine of soybean Leghemoglobin. Effects of nicotinate and other heme ligands.

Cited by 39 publications

References 28 publications

NMR titration curves of histidine ring protons. 11. Near-heme histidine residues of deoxy- and oxymyoglobins

NMR titration curves of histidine ring protons. 11. Near-heme histidine residues of deoxy- and oxymyoglobins

Resonance Raman investigations of site-directed mutants of myoglobin: effects of distal histidine replacement

A study of ligand binding to spleen myeloperoxidase

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