Direct assignment of vitamin K1 as the secondary acceptor A1 in photosystem I.
The characteristic electron spin polarized electron paramagnetic resonance (ESP EPR) signal observed in photosystem I (PSI) has been previously assigned to a radical pair composed of the oxidized primary donor and a reduced vitamin K1. Under conditions in which Bottin, H. & Setif, P. [(1991), Biochim. Biophys. Acta 105, 331-336] proposed that A1 is doubly reduced, the ESP EPR signal was not observed. Therefore, the ESP EPR signal can be directly attributed to A-1, and vitamin K1 can be assigned as this PSI acceptor. The ESP EPR signal was partially restored by removal of the chemical reductants.
Snyder
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SW
Chemistry Division, Argonne National Laboratory, Argonne, IL 60439, USA.
Rustandi
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RR
Biggins
J
J
Norris
J R
JR
Thurnauer
M C
MC