Abstract
The reaction center (RC) of heliobacteria seems to have evolved from an ancestor common with photosystem (PS) I RC of cyanobacteria and plants. However, the reaction of quinone that is obvious in PS I heterodimeric RC has never been evidenced in heliobacterial RC. The RC as well as that of green sulfur bacteria, which is also type-1, are considered to form the symmetrical homodimeric structure. We previously showed the FX signal in membranes for the first time and carried out comparative analyses of flash-induced absorption changes between membranes and core protein from Heliobacterium modesticuldum. As the crude RC preparation with a different method was isolated, we here report flash-induced absorption changes and ESR measurements. The P798+, formed immediately after flash excitation, was recovered with a t1/2 = 30 ms, suggesting the back reaction from the terminal electron acceptor FA/FB. In fact, we detected Fe-S centers A/B signals in ESR spectroscopy.
