Elucidating the role of the ci heme in photosynthetic cytochrome b6f complexes: a key element at a crossroad of electron transfer and regulatory processes – HemeMotion

Advancing knowledge on bioenergetics is the key to identifying opportunities for improving the performance of the catalytic enzymes involved in photosynthesis. Here we propose to elucidate the role of a cofactor present in the chloroplast cytochrome b6f complex which is missing in the mitochondrial cytochrome bc1 complex. Because oxygen is produced by photosynthesis in the chloroplast and consumed by respiration in the mitochondrion, the oxygen tension is much higher in the former than it is in the latter. We believe heme ci is required in the chloroplast to avoid the formation of reactive oxygen species. Based on our preliminary unpublished work (new SD mutants, new time-resolved spectrophotometers, new measuring chambers) we think we can show the molecular mechanism of concerted reduction and protonation of the quinone avoiding the harmful semi-quinone state. This would put into perspective the ambitions we have made to make photosynthesis more robust and more efficient.