Electrostatic role of the non-heme iron complex in bacterial photosynthetic reaction center.
To elucidate the role of the non-heme iron complex (Fe-complex) in the electron transfer (ET) events of bacterial photosynthetic reaction centers (bRC), we calculated redox potentials of primary/secondary quinones Q(A/B) (E(m)(Q(A/B))) in the Fe-depleted bRC. Removing the Fe-complex, the calculated E(m)(Q(A/B)) are downshifted by approximately 220 mV/ approximately 80 mV explaining both the 15-fold decrease in ET rate from bacteriopheophytin (H(A)(-)) to Q(A) and triplet state occurrence in Fe-depleted bRC. The larger downshift in E(m)(Q(A)) relative to E(m)(Q(B)) increases the driving-energy for ET from Q(A) to Q(B) by 140 meV, in agreement with approximately 100 meV increase derived from kinetic studies.
Ishikita
Hiroshi
H
Institute of Chemistry and Biochemistry, Free University of Berlin, Takustrasse 6, D-14195 Berlin, Germany. hiro@chemie.fu-berlin.de
Knapp
Ernst-Walter
EW
D001426:Bacterial Proteins / Q000737:chemistry*; D004579:Electron Transport; D019159:Nonheme Iron Proteins / Q000737:chemistry*; D010084:Oxidation-Reduction; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry*; D011809:Quinones / Q000737:chemistry; D055672:Static Electricity
D001426:Bacterial Proteins; D019159:Nonheme Iron Proteins; D045322:Photosynthetic Reaction Center Complex Proteins; D011809:Quinones