Positions of QA and ChlZ relative to tyrosine YZ and YD in photosystem II studied by pulsed EPR

Abstract

PELDOR (Pulsed Electron eLectron DOuble Resonance) was applied to determine the distance of between YZ and QA- in YD-less mutant of Chlamydomonas reinhardtii in Tris-treated and Zn-substituted preparation of photosystem II. The value of distance was found to be 34.5 ± 1 Å. A '2 + 1' electron spin echo method has been applied to measure the orientation of the radius-vector R fom YD to ChlZ in a membrane-oriented photosystem II. The angle between R and the membrane normal n was determined to be 50 ± 5°, using the distance 29.4 ± 0.5 Å determined in non-oriented PS II.