The Isolation of a Functional Cytochrome b (6) f Complex: from Lucky Encounter to Rewarding Experiences.

The recognition that, in photosynthesis, the plastoquinol oxidizing cytochrome b (6f ) complex resembles the ubiquinol oxidizing cytochrome bc1 complex in respiration is one of the examples of exciting universalization in biological research. A peripheral observation towards the end of 1979 initiated an intensive investigation, which is still ongoing today: next to the ATP synthase the cytochrome b (6f ) complex could be selectively solubilized from the chloroplast membrane by the combined action of octyl glucoside and cholate. It was mere luck that the isolate was substantially active as an electrogenic, proton translocating plastoquinol-plastocyanin oxidoreductase, and that it also catalyzed oxidant-induced reduction of cytochrome b (6), a signature of the Q-cycle mechanism. The basic findings during the first characterization of the complex are summarized, and the excitement among the collaborating groups is remembered. More recent developments, including the impact of gene technology and the elucidation by the crystal structure, are additionally traced here.