Structural features of the copper‐depleted cytochrome oxidase from beef heart: iron exafs

Powers, Linda S.; Chance, Britton; Ching, Yuan-Chin; Muhoberac, Barry B.; Weintraub, Susan T.; Wharton, David C.

doi:10.1016/0014-5793(82)80452-3

Cited by 14 publications

(10 citation statements)

References 19 publications

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“…Lengthening of the pyrrole nitrogen distance is also supported by the shift of the absorption edge of 2 eV to lower energy on photolysis. Similar shifts are observed in model compounds and other heme proteins where this expansion is known regardless of the chemical type of axial ligands (Powers et al, 1982;Korszun & Moffit, 1982;Labhardt & Yuen, 1972). In addition, the fitting procedures for the chemical deoxy state yield an average Fe-Np distance of 2.06 ± 0.02 Á with Fe-Nf distance of 2.12 ± 0.02 Á in agreement with Takano (1977).…”

Section: Resultssupporting

confidence: 60%

“…The X-ray absorption data were analyzed by procedures discussed previously (Powers et al, 1979(Powers et al, , 1981(Powers et al, , 1982Lee et al, 1981;Peisach et al, 1982). Short scans (Figure 4) covering a 7050-7250-eV energy range were collected in 4 min each by measuring two points below the edge (2 s each), 17 points over the edge maximum (1 s each), and 59 points (4 s each) in the energy range above the edge.…”

Section: Methodsmentioning

confidence: 99%

“…A method affording measurement of structural changes of Mb*CO with respect to Mb and MbCO was required, and in 1979 the first data were obtained at 4 K by the extended X-ray absorption fine structure (EXAFS) method, which determines alterations in the distances of the first, second, and third shell ligands of iron porphyrins (Chance & Powers, 1981a,b;Fischetti et al, 1981), as first used in the study of hemoglobin (Eisenberger et al, 1978) and more recently of cytochrome oxidase (Powers et al, 1981(Powers et al, , 1982Chance & Powers, 1981a;Chance et al, 1980a). The findings have been consistent since the early observation, indicating small structural changes on photolysis and pointing, for the first time, to the possibility that the ligand remains close to the iron atom and that the Fe-Np(pyrrole) distances lengthen characteristic of the change from MbCO to Mb is incomplete.…”

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confidence: 99%

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Structure and kinetics of the photoproduct of carbonylmyoglobin at low temperatures; an x-ray absorption study

1983

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Photolysis and recombination of carboxymyoglobin at low temperatures have been studied by a variety of methods. This paper combines optical and structural studies of carboxymyoglobin photolysis and recombination in the temperature range 4-120 K. The absorbance changes indicate ablation of the characteristic optical transitions of carboxymyoglobin and formation of a photoproduct (Mb*CO) differing from deoxymyoglobin. When the X-ray absorption changes in the 7150-7200-eV region of the X-ray absorption spectrum are used as an indicator of structural change, the photoproduct at 4 K as measured with respect to the unphotolyzed sample is 60% of that observed for the chemically produced deoxy form. Saturation of the change is obtained with repetitive flashes totaling several thousand joules of energy from a xenon flash lamp by using a thin sample (1 mm) at 4 mM concentration as measured by both optical transmission and X-ray absorption criteria. The kinetics of the reaction show the change to occur at 10 K within the resolving time currently available (2 s) in the X-ray absorption measurements. The amplitude of the light-induced change decreases to half its maximal value at 40 K and to zero at 90 K. Steady illumination suggests at least two recombination processes. Analysis of the extended X-ray absorption fine structure (EXAFS) data on Mb*CO indicates small distance changes in the first shell of Fe-N and Fe-C that can be attributed to lengthening of the pyrrole nitrogen bonds and proximal histidine motion, together with a small displacement of the CO molecule on photolysis--a form here designated Mb*CO. This structure of the germinate state, Mb*CO, may elucidate the nature of elementary steps in chemical reactions and in tunneling processes.

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Section: Resultssupporting

confidence: 60%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Structure and kinetics of the photoproduct of carbonylmyoglobin at low temperatures; an x-ray absorption study

1983

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“…Proceeding to analyze the pulsed form in this manner with the same models as used previously (14), the third shell of the copper data of the pulsed oxidase (Fig. 4) contains a single iron atom at 3.83 ± 0.05 A while the iron third shell contains a single copper atom at this distance, together with outer shell heme contributions that are nearly identical to the outer shell heme contributions found in the resting oxidized (14) and copper-depleted forms (25). Amplitude comparisons of these contributions with that of the resting oxidized form show little change in the Debye-Waller contribution, AaXT2 = -1.5 x 10-3 A2, indicating that this structure may be only slightly less rigid than that of the resting oxidized form.…”

Section: Resultsmentioning

confidence: 82%

“…The site modeling method is sensitive to changes in the geometry (distances) or one ligand of the model, as has been demonstrated by the differences in the edge data and first shell filtered data of both heme and copper complexes (14,(22)(23)(24)(25). Further, the model must represent the site in all redox states (e.g., oxidized model = oxidized site, reduced model = reduced site) as previously applied to both edge and EXAFS cytochrome oxidase data (14, 24); hence, all observed states must be self-consistent.…”

Section: X-ray Absorption Methodsmentioning

confidence: 99%

"Peroxidatic" form of cytochrome oxidase as studied by X-ray absorption spectroscopy

Chance¹,

Kumar²,

Powers³

et al. 1983

Biophysical Journal

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X-ray absorption spectroscopy shows pulsed oxidase to be similar to resting oxidase but to lack the sulfur bridge between iron and copper of active sites (Powers, L., Y. Ching, B. Chance, and B. Muhoberac, 1982, Biophys. J., 37[2, Pt. 2]: 403a. [Abstr.] ) The first shell ligands and bond lengths of the pulsed oxidase active site heme most clearly fit the ferric peroxidases from horseradish and yeast, and the pulsed oxidase cyanide compound resembles the low spin hemoprotein cyanide compounds. The structural results are consistent with an aquo or a peroxo form for pulsed oxidase as is also observed by optical studies. These structural and chemical data are consistent with a role for the pulsed forms in a cyclic peroxidatic side reaction in which the pulsed and pulsed peroxide compounds act as peroxide scavengers. The peroxidatic role of cytochrome oxidase in the nonsulfur bridged form suggests the renaming of the "oxygenated" or "pulsed" forms on a functional basis as "peroxidatic" forms of cytochrome oxidase.

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Oxidases

Ingraham¹,

Meyer²

1985

Biochemistry of Dioxygen

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Structural features of the copper‐depleted cytochrome oxidase from beef heart: iron exafs

Cited by 14 publications

References 19 publications

Structure and kinetics of the photoproduct of carbonylmyoglobin at low temperatures; an x-ray absorption study

Structure and kinetics of the photoproduct of carbonylmyoglobin at low temperatures; an x-ray absorption study

"Peroxidatic" form of cytochrome oxidase as studied by X-ray absorption spectroscopy

Oxidases

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