Portal de Periódicos da CAPES

How photosynthetic reaction centers control oxidation power in chlorophyll pairs P680, P700, and P870

2006; National Academy of Sciences; Volume: 103; Issue: 26 Linguagem: Inglês

10.1073/pnas.0601446103

1091-6490

Hiroshi Ishikita, Wolfram Saenger, Jacek Biesiadka, Bernhard Loll, Ernst‐Walter Knapp,

Photoreceptor and optogenetics research

At the heart of photosynthetic reaction centers (RCs) are pairs of chlorophyll a (Chl a ), P700 in photosystem I (PSI) and P680 in photosystem II (PSII) of cyanobacteria, algae, or plants, and a pair of bacteriochlorophyll a (BChl a ), P870 in purple bacterial RCs (PbRCs). These pairs differ greatly in their redox potentials for one-electron oxidation, E m . For P680, E m is 1,100–1,200 mV, but for P700 and P870, E m is only 500 mV. Calculations with the linearized Poisson–Boltzmann equation reproduce these measured E m differences successfully. Analyzing the origin for these differences, we found as major factors in PSII the unique Mn 4 Ca cluster (relative to PSI and PbRC), the position of P680 close to the luminal edge of transmembrane α-helix d (relative to PSI), local variations in the cd loop (relative to PbRC), and the intrinsically higher E m of Chl a compared with BChl a (relative to PbRC).