FLASH-INDUCED ELECTROGENIC REACTIONS IN THE SA(L223) REACTION-CENTER MUTANT IN RHODOBACTER-SPHAEROIDES CHROMATOPHORES

The charge transfer events in the SA(L223) reaction center mutant Rhodobacter sphaeroides chromatophores were investigated by direct electrometry. Besides the primary charge separation, the small stigmatellin-sensitive electrogenic reaction due to the electron transfer from the primary to the secondary quinone acceptor in the reaction center complex was observed after the first hash. The second flash-induced electrogenic phase of the secondary quinone protonation and subsequent electrogenic reactions of the cytochrome be, complex were much slower than those in chromatophores of the wild type. It is suggested that replacement of Ser-L223 by Ala impairs both specific proton-conducting pathways leading to the secondary quinone Q(B).