Fig. 1.

Schematic model of cyanobacterial thylakoid membrane (based on knowledge of Synechocystis 6803 thylakoids), showing the interplay of photosynthetic and respiratory electron transport component in the same membrane. Photosynthetic electron transfer complexes include phycobilisome, PSII and PSI, cyt b₆f and ATPase. The presence of phycobilisome–photosystem supercomplex in vivo has been identified [38], [39]. Complexes specific for respiratory electron transport chain are NDH-1, SDH and cyt oxidase. Some components, such as the cyt b₆f, PQ and PC are shared by both electron transport pathways. There are also potassium channel proteins in the thylakoid membrane. Arrows indicate the electron transduction reactions. Abbreviations: ADP — adenosine diphosphate, ATP — adenosine triphosphate, cyt b₆f — cytochrome b₆f, cyt c₆ — cytochrome c₆, cyt oxidase — cytochrome oxidase, NADP(H) — nicotinamide-adenine dinucleotide phosphate (reduced form), NDH-1 — type 1 NADPH dehydrogenase, PC — plastocyanin, PQ — plastoquinone, SDH — succinate dehydrogenase. The protein structures are achieved from PDB database: allophycocyanin, PDB ID: 1KN1; NDH-1, based on the Complex I structure from Thermus thermophilus, PDB ID: 4HEA; cyt b₆f, PDB ID: 4H13; cyt oxidase, PDB ID: 1OCO; potassium channel protein, based on the Magnetospirillum magnetotacticum KirBac3.1 potassium channel crystal structure, PDB ID: 1XL4; phycocyanin, PDB ID: 3O18; PSI, PDB ID: 1JB0; PSII, PDB ID: 3WU2; and SDH, based on the E. coli SDH crystal structures, PDB ID: 1NEK.