Spectroelectrochemistry of cytochrome b559 in the D1-D2-Cyt b559 complex from spinach
Tadao Shibamoto1, Yuki Kato, Tadashi Watanabe
1Institute of Industrial Science, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8505, Japan.
Abstract:
The redox potential of cytochrome b559 (Cyt b559) in the D1-D2-Cyt b559 complex from spinach has been determined to be +90+/-2mV vs. SHE at pH 6.0, by thin-layer cell spectroelectrochemistry for the first time. The redox potential, corresponding uniquely to the so-called "low-potential form", exhibited a sigmoidal pH-dependence from pH 4.0 to 9.0, ranging from +115 to +50mV. An analysis of the pH-dependence based on model equations suggests that two histidine residues coordinating to the heme iron in the protein subunits may exert electrostatic influence on the redox potential of Cyt b559.
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