Molecular variants of Golfingia gouldii hemerythrin. Primary structure of the variants arising from five amino acid interchanges

Gl, Klippenstein

doi:10.1021/bi00753a011

Cited by 34 publications

(10 citation statements)

References 34 publications

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“…Analysis of the chymotryptic peptide maps of control and photooxidized hemerythrin indicates that histidine-82 and -34 are photooxidized and are therefore not likely iron ligands. These results are in agreement with the X-ray studies previously cited as well as the fact that these two residues are variable between different hemerythrins (Klippenstein, 1972;Ferrell & Kitto, 1971;Klippenstein et al, 1976;Loehr et al, 1978); yet the active-site spectrum is constant. Our results also indicate that histidine-25, -54, and -101 are definitely not photooxidized, a conclusion consistent with their role as iron ligands as deduced from both X-ray studies.…”

Section: Discussionsupporting

confidence: 92%

Proton magnetic resonance study of the histidines in hemerythrin and chemical identification of the nonligand histidines

York¹,

Millett²,

Minor³

1980

Biochemistry

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Three non-iron-liganded histidines have been studied in methemerythrin azide monomers from Pascolopsis gouldii by 250-MHz proton correlation nuclear magnetic resonance (NMR) spectroscopy. Four of the seven histidines in the protein are not observed because of paramagnetic broadening by the coordinated iron; neither are they observed as contact or pseudocontact shifted resonances. The NMR titration of the three free histidines establishes them as normal histidines with pK' values of 7.00 +/- 0.03 and Hill coefficients of 0.90, 0.81, and 0.81 +/- 0.03. The chemical shift of the protonated and neutral histidines is normal, and the bandwidth of the resonance absorption is 5 Hz. A pH-dependent reversible transition in the chemical shift of the histidine C(2)H occurs at pH 6.5; above this pH the three protons occur as a singlet but break into three singlets of different chemical shift at acid pH values. Two of the three "free" histidines have been identified by their susceptibility to photooxidation as His-82 and His-34.

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Section: Discussionsupporting

confidence: 92%

Proton magnetic resonance study of the histidines in hemerythrin and chemical identification of the nonligand histidines

York¹,

Millett²,

Minor³

1980

Biochemistry

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“…The derived amino acid sequence was identical to that published for one of the minor amino acid variants of native P. gouldii Hr in which a threonine is substituted for a glycine at position 79 (26). Native P. gouldii Hr consists of a total of five amino acid substitution variants in varying proportions; none of these variants is known to affect any spectroscopic or functional properties of the di-iron site (27).…”

Section: Isolation Of the Recombinant P Gouldii Hrs-the P Gouldiimentioning

confidence: 87%

A Leucine Residue “Gates” Solvent but Not O2Access to the Binding Pocket of Phascolopsis gouldiiHemerythrin

Farmer¹,

Kurtz²,

Phillips³

et al. 2000

Journal of Biological Chemistry

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A leucine residue, Leu-98, lines the O 2 -binding pocket in all known hemerythrins. Leu-98 in recombinant Phascolopsis gouldii hemerythrin, was mutated to several other residues of varying sizes (Ala, Val), polarities (Thr, Asp, Asn), and aromaticities (Phe, Tyr, Trp). UVvisible and resonance Raman spectra showed that the di-iron sites in these L98X Hrs are very similar to those in the wild type protein, and several of the L98X hemerythrins formed stable oxy adducts. Despite the apparently tight packing in the pocket, all of the L98X Hrs except for L98W, had second order O 2 association rate constants within a factor of 3 of the wild type value. Similarly, the O 2 dissociation rate constant was essentially unaffected by substitutions of larger (Phe) or smaller (Val, Thr) residues for Leu-98. L98Y Hr showed a 170-fold decrease in the O 2 dissociation rate constant and a large D 2 O effect on this rate, which are attributed to a hydrogen-bonding interaction between the Tyr-98 hydroxyl and the bound O 2 . Significant increases in autoxidation rates were observed for all of the L98X Hrs other than X ‫؍‬ Tyr. These increases in autoxidation rates are attributed to increased solvent access to the binding pocket caused by inefficient packing (Phe), smaller size (Val, Ala), or increased polarity (Thr, Asp, Asn) of the residue 98 side chain. A leucine at position 98 appears to have the optimal size, shape, and hydrophobicity for inhibition of solvent access. Thus, "gating" of small molecule access to the binding pocket of Hr by Leu-98 is not evident for O 2 , but is evident for solvent.

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“…The methemerythrin derived from T. pyroides is some 20 times more reactive than that from P. gouldii, a relative reactivity which we have found displayed toward inorganic reactants, although rarely as pronounced. The primary structure of T. pyroides myohemerythrin (Klippenstein et al, 1976) differs from the coelomic hemerythrin of T. pyroides (Ferrell & Kitto, 1971) in 60 residue positions, whereas the coelomic hemerythrin of T. pyroides and P. gouldii (Klippenstein, 1972;Klippenstein et al, 1968) differs in only four positions. Most, if not all, of the iron-coordinated ligands are the same, however, in all species (Stenkamp et al, 1976b(Stenkamp et al, , 1978 and this must be paramount in defining reactivity.…”

Section: Discussionmentioning

confidence: 97%

Reduction of methemerythrin by deoxymyoglobin: a protein-protein redox reaction not involving electron-transfer proteins

Bradić¹,

Harrington²,

Wilkins³

1979

Biochemistry

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The stoichiometry and kinetics of reaction of methemerythrin with the deoxy forms of myoglobin and hemoglobin have been examined at I = 0.2 M and 25 degrees C. One mole of methemerythrin (on the basis of the monomer unit containing two irons) reacts with 2 mol of deoxymyoglobin and with 0.5 mol of deoxyhemoglobin. All reactions are second order. Rate constants for reaction with deoxymyoglobin are 0.25 M-1s-1 (Phascolopsis gouldii) and 5.6 M-1s-1 (Themiste pyroides) at pH 6.3. There is little effect of raising the ionic strength to 1.35 M and only a small decrease in rate when the pH is adjusted to 8.2. The rate constant for reaction of deoxyhemoglobin with P. gouldii methemerythrin is approximately 0.1 M-1s-1 at pH 6.3. Metmyohemerythrin from T. pyroides reacts slightly slower than the octamer form (k = 2.0 M-1s-1 at pH 6.3 and 7.0). Oxymyoglobin is converted to metmyoglobin by methemerythrin. The electron-transfer path is discussed and a self-exchange rate constant for hemerythrin assessed as 10(-3) M-1s-1 on the basis of Marcus's theory.

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Molecular variants of Golfingia gouldii hemerythrin. Primary structure of the variants arising from five amino acid interchanges

Cited by 34 publications

References 34 publications

Proton magnetic resonance study of the histidines in hemerythrin and chemical identification of the nonligand histidines

Proton magnetic resonance study of the histidines in hemerythrin and chemical identification of the nonligand histidines

A Leucine Residue “Gates” Solvent but Not O2Access to the Binding Pocket of Phascolopsis gouldiiHemerythrin

Reduction of methemerythrin by deoxymyoglobin: a protein-protein redox reaction not involving electron-transfer proteins

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