The position of cytochrome b(559) relative to Q(A) in photosystem II studied by electron-electron double resonance (ELDOR).
The electron-electron double resonance (ELDOR) method was applied to measure the dipole interaction between cytochrome (Cyt) b(+)(559) and the primary acceptor quinone (Q(-)(A)), observed at g=2.0045 with the peak to peak width of about 9 G, in Photosystem II (PS II) in which the non-heme Fe(2+) was substituted by Zn(2+). The paramagnetic centers of Cyt b(+)(559)Y(D)Q(-)(A) were trapped by illumination at 273 K for 8 min, followed by dark adaptation for 3 min and freezing into 77 K. The distance between the pair Cyt b(+)(559)-Q(-)(A) was estimated from the dipole interaction constant fitted to the observed ELDOR time profile to be 40+/-1 A. In the membrane oriented PS II particles the angle between the vector from Q(A) to Cyt b(559) and the membrane normal was determined to be 80+/-5 degrees. The position of Cyt b(559) relative to Q(A) suggests that the heme plane is located on the stromal side of the thylakoid membrane. ELDOR was not observed for Cyt b(+)(559) Y(D) spin pair, suggesting the distance between them is more than 50 A.
Kuroiwa
S
S
Faculty of Science, Kwansei Gakuin University, Uegahara 1-1-155, Nishinomiya 662-8501, Japan.
Tonaka
M
M
Kawamori
A
A
Akabori
K
K
D002413:Cations, Divalent; D003573:Cytochrome b Group / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D007501:Iron / Q000737:chemistry; D008433:Mathematics; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry*; D045332:Photosystem II Protein Complex; D015032:Zinc / Q000737:chemistry
D002413:Cations, Divalent; D003573:Cytochrome b Group; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; C019313:cytochrome b559; D007501:Iron; D015032:Zinc