Does cytochrome-c oxidase exist in both low- and high-spin pulsed forms?

1989 ◽  
Vol 17 (5) ◽  
pp. 897-898
Author(s):  
NIKOLAUS IOANNIDIS ◽  
JOHN M. WRIGGLESWORTH
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
High Spin

scholarly journals Near-infrared magnetic and natural circular dichroism of cytochrome c oxidase

1980 ◽  
Vol 191 (2) ◽  
pp. 319-331 ◽  
Author(s):  
D G Eglinton ◽  
M K Johnson ◽  
A J Thomson ◽  
P E Gooding ◽  
C Greenwood
Keyword(s):  
Cytochrome C ◽  
Absorption Band ◽  
Cytochrome C Oxidase ◽  
High Spin ◽  
Room Temperature ◽  
Near Infrared ◽  
Sodium Dithionite ◽  
Cyanide Ion ◽  
Reduced State

A detailed study is presented of the room-temperature absorption, natural and magnetic circulation-dichroism (c.d. and m.c.d.) spectra of cytochrome c oxidase and a number of its derivatives in the wavelength range 700-1900 nm. The spectra of the reduced enzyme show a strong negative c.d. band peaking at 1100nm arising from low-spin ferrous haem a and a positive m.c.d. peak at 780nm assigned to high-spin ferrous haem a3. Addition of cyanide ion doubles the intensity of the low-spin ferrous haem c.d. band and abolishes reduced carbonmonoxy derivative the haem a32+-CO group shows no c.d. or m.c.d. bands at wavelengths longer than 700nm. A comparison of the m.c.d. spectra of the oxidized and cyanide-bound oxidized forms enables bands characteristic of the high-spin ferric form of haem a33+ to be identified between 700 and 1300nm. At wavelengths longer than 1300nm a broad positive m.c.d. spectrum, peaking at 1600nm, is observed. By comparison with the m.c.d. spectrum of an extracted haem a-bis-imidazole complex this m.c.d. peak is assigned to one low-spin ferric haem, namely haem a3+. On binding of cyanide to the oxidized form of the enzyme a new, weak, m.c.d. signal appears, which is assigned to the low-spin ferric haem a33+-CN species. A reductive titration, with sodium dithionite, of the cyanide-bound form of the enzyme leads to a partially reduced state in which low-spin haem a2+ is detected by means of an intense negative c.d. peak at 1100 nm and low-spin ferric haem a33+-CN gives a sharp positive m.c.d. peak at 1550nm. The c.d. and m.c.d. characteristics of the 830nm absorption band in oxidized cytochrome c oxidase are not typical of type 1 blue cupric centres.

scholarly journals Variable-temperature magnetic-circular-dichroism spectra of cytochrome c oxidase and its derivatives

1977 ◽  
Vol 165 (2) ◽  
pp. 327-336 ◽  
Author(s):  
Andrew J. Thomson ◽  
Thomas Brittain ◽  
Colin Greenwood ◽  
John P. Springall
Keyword(s):  
Circular Dichroism ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
High Spin ◽  
Magnetic Circular Dichroism ◽  
Variable Temperature ◽  
Effect Of Temperature ◽  
Circular Dichroism Spectra ◽  
Circular Dichroïsm ◽  
Magnetic Circular Dichroism Spectra

A detailed study of the effect of temperature on the m.c.d. (magnetic circular dichroism) spectra of cytochrome c oxidase and some of its derivatives was undertaken to characterize the spin states of haem a and a3. The fully reduced enzyme contains haem a32+in its high-spin form and haem a2+in the low-spin state. This conclusion is reached by comparing the spectrum with that of the mixed-valence CO derivatives and its photolysis product. The cyanide derivative of the fully reduced enzyme contains both haem a and a3 in the low-spin ferrous form. The m.c.d. spectra of the fully oxidized derivatives are consistent with the presence of one low-spin ferric haem group, assigned to a, which remains unaltered in the presence of ligands. Haem a3 is high spin in the resting enzyme and the fluoride derivatives, and low spin in the cyanide form. The partially reduced formate and cyanide derivatives have temperature-dependent m.c.d. spectra due to the presence of high- and low-spin haem a33+respectively. Haem a is low-spin ferrous in both. A comparison of the magnitude of the temperature-dependence of haem a33+in the fully oxidized and partially reduced forms shows a marked difference which is tentatively ascribed to the presence of anti-ferromagnetic coupling in the fully oxidized form of the enzyme, and to its absence from the partially reduced derivatives, owing to the reduction of both Cu2+ions.

scholarly journals Formation of high spin cytochrome a in isolated cytochrome c oxidase.

1993 ◽  
Vol 268 (7) ◽  
pp. 4716-4719
Author(s):  
S.A. Walter ◽  
P.G. Papadopoulos ◽  
G.M. Baker
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
High Spin
Sign in / Sign up

Export Citation Format

Share Document