Structural features and the reaction mechanism of cytochrome oxidase; iron and copper X-ray absorption fine structure

Linda S Powers, B. Chance, Y. Ching, P. Angiolillo

Research output: Contribution to journalArticle

191 Citations (Scopus)

Abstract

X-ray edge absorption of copper and extended fine structure studies of both copper and iron centers have been made of cytochrome oxidase from beef heart, Paracoccus dentrificans, and HB-8 thermophilic bacteria (1-2.5 mM in heme). The desired redox state (fully oxidized, reduced CO, mixed valence formate and CO) in the x-ray beam was controlled by low temperature (-140°C) and was continuously monitored by simultaneous optical spectroscopy and by electron paramagnetic resonance (EPR) monitoring every 30 min of x-ray exposure. The structure of the active site, a cytochrome α3-copper pair in fully oxidized and in mixed valence formate states where they are spin coupled, contains a sulphur bridge with three ligands 2.60 ± 0.03 Å from Fe(α3) and 2.18 ± 0.03 Å from Cu(α3). The distance between Fe(α3) and Cu(α3) is 3.75 ± 0.05 Å, making the sulphur bond angle 103° reasonable for sp3 sulphur bonding. The Fe(α3) first shell has four typical heme nitrogens (2.01 ± 0.03 Å) with a proximal nitrogen at 2.14 ± 0.03 Å. The sixth ligand is the bridging sulphur. The Cu(α3) first shell is identical to oxidized stellacyanin containing two nitrogens and a bridging sulphur. Upon reduction with CO, the active site is identical to reduced stellacyanin for the Cu(α3) first shell and contains the sulphur that forms the bridge in fully oxidized and mixed valence formate states. The Fe(α3) first shell is identical to oxyhemoglobin but has CO instead of O2. The other redox centers, Fe(α) and the other 'EPR detectable' Cu are not observed in higher shells of Fe(α3). Fe(α) has six equidistant nitrogens and Cu(α) has one (or two) nitrogens and three (or two) sulphurs with typical distances; these ligands change only slight on reduction. These structures afford the basis for an oxygen reduction mechanism involving oxy- and peroxy intermediates.

Original languageEnglish (US)
Pages (from-to)465-498
Number of pages34
JournalBiophysical Journal
Volume34
Issue number3
StatePublished - 1981
Externally publishedYes

Fingerprint

Electron Transport Complex IV
formic acid
Sulfur
Copper
Iron
X-Rays
Carbon Monoxide
Nitrogen
Electron Spin Resonance Spectroscopy
Ligands
Heme
Oxidation-Reduction
Catalytic Domain
Cytochromes a3
Paracoccus
Oxyhemoglobins
Spectrum Analysis
Oxygen
Bacteria
Temperature

ASJC Scopus subject areas

  • Biophysics

Cite this

Structural features and the reaction mechanism of cytochrome oxidase; iron and copper X-ray absorption fine structure. / Powers, Linda S; Chance, B.; Ching, Y.; Angiolillo, P.

In: Biophysical Journal, Vol. 34, No. 3, 1981, p. 465-498.

Research output: Contribution to journalArticle

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abstract = "X-ray edge absorption of copper and extended fine structure studies of both copper and iron centers have been made of cytochrome oxidase from beef heart, Paracoccus dentrificans, and HB-8 thermophilic bacteria (1-2.5 mM in heme). The desired redox state (fully oxidized, reduced CO, mixed valence formate and CO) in the x-ray beam was controlled by low temperature (-140°C) and was continuously monitored by simultaneous optical spectroscopy and by electron paramagnetic resonance (EPR) monitoring every 30 min of x-ray exposure. The structure of the active site, a cytochrome α3-copper pair in fully oxidized and in mixed valence formate states where they are spin coupled, contains a sulphur bridge with three ligands 2.60 ± 0.03 {\AA} from Fe(α3) and 2.18 ± 0.03 {\AA} from Cu(α3). The distance between Fe(α3) and Cu(α3) is 3.75 ± 0.05 {\AA}, making the sulphur bond angle 103° reasonable for sp3 sulphur bonding. The Fe(α3) first shell has four typical heme nitrogens (2.01 ± 0.03 {\AA}) with a proximal nitrogen at 2.14 ± 0.03 {\AA}. The sixth ligand is the bridging sulphur. The Cu(α3) first shell is identical to oxidized stellacyanin containing two nitrogens and a bridging sulphur. Upon reduction with CO, the active site is identical to reduced stellacyanin for the Cu(α3) first shell and contains the sulphur that forms the bridge in fully oxidized and mixed valence formate states. The Fe(α3) first shell is identical to oxyhemoglobin but has CO instead of O2. The other redox centers, Fe(α) and the other 'EPR detectable' Cu are not observed in higher shells of Fe(α3). Fe(α) has six equidistant nitrogens and Cu(α) has one (or two) nitrogens and three (or two) sulphurs with typical distances; these ligands change only slight on reduction. These structures afford the basis for an oxygen reduction mechanism involving oxy- and peroxy intermediates.",
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N2 - X-ray edge absorption of copper and extended fine structure studies of both copper and iron centers have been made of cytochrome oxidase from beef heart, Paracoccus dentrificans, and HB-8 thermophilic bacteria (1-2.5 mM in heme). The desired redox state (fully oxidized, reduced CO, mixed valence formate and CO) in the x-ray beam was controlled by low temperature (-140°C) and was continuously monitored by simultaneous optical spectroscopy and by electron paramagnetic resonance (EPR) monitoring every 30 min of x-ray exposure. The structure of the active site, a cytochrome α3-copper pair in fully oxidized and in mixed valence formate states where they are spin coupled, contains a sulphur bridge with three ligands 2.60 ± 0.03 Å from Fe(α3) and 2.18 ± 0.03 Å from Cu(α3). The distance between Fe(α3) and Cu(α3) is 3.75 ± 0.05 Å, making the sulphur bond angle 103° reasonable for sp3 sulphur bonding. The Fe(α3) first shell has four typical heme nitrogens (2.01 ± 0.03 Å) with a proximal nitrogen at 2.14 ± 0.03 Å. The sixth ligand is the bridging sulphur. The Cu(α3) first shell is identical to oxidized stellacyanin containing two nitrogens and a bridging sulphur. Upon reduction with CO, the active site is identical to reduced stellacyanin for the Cu(α3) first shell and contains the sulphur that forms the bridge in fully oxidized and mixed valence formate states. The Fe(α3) first shell is identical to oxyhemoglobin but has CO instead of O2. The other redox centers, Fe(α) and the other 'EPR detectable' Cu are not observed in higher shells of Fe(α3). Fe(α) has six equidistant nitrogens and Cu(α) has one (or two) nitrogens and three (or two) sulphurs with typical distances; these ligands change only slight on reduction. These structures afford the basis for an oxygen reduction mechanism involving oxy- and peroxy intermediates.

AB - X-ray edge absorption of copper and extended fine structure studies of both copper and iron centers have been made of cytochrome oxidase from beef heart, Paracoccus dentrificans, and HB-8 thermophilic bacteria (1-2.5 mM in heme). The desired redox state (fully oxidized, reduced CO, mixed valence formate and CO) in the x-ray beam was controlled by low temperature (-140°C) and was continuously monitored by simultaneous optical spectroscopy and by electron paramagnetic resonance (EPR) monitoring every 30 min of x-ray exposure. The structure of the active site, a cytochrome α3-copper pair in fully oxidized and in mixed valence formate states where they are spin coupled, contains a sulphur bridge with three ligands 2.60 ± 0.03 Å from Fe(α3) and 2.18 ± 0.03 Å from Cu(α3). The distance between Fe(α3) and Cu(α3) is 3.75 ± 0.05 Å, making the sulphur bond angle 103° reasonable for sp3 sulphur bonding. The Fe(α3) first shell has four typical heme nitrogens (2.01 ± 0.03 Å) with a proximal nitrogen at 2.14 ± 0.03 Å. The sixth ligand is the bridging sulphur. The Cu(α3) first shell is identical to oxidized stellacyanin containing two nitrogens and a bridging sulphur. Upon reduction with CO, the active site is identical to reduced stellacyanin for the Cu(α3) first shell and contains the sulphur that forms the bridge in fully oxidized and mixed valence formate states. The Fe(α3) first shell is identical to oxyhemoglobin but has CO instead of O2. The other redox centers, Fe(α) and the other 'EPR detectable' Cu are not observed in higher shells of Fe(α3). Fe(α) has six equidistant nitrogens and Cu(α) has one (or two) nitrogens and three (or two) sulphurs with typical distances; these ligands change only slight on reduction. These structures afford the basis for an oxygen reduction mechanism involving oxy- and peroxy intermediates.

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