text: In cyanobacteria, inorganic phosphate (P) also participates in the co-ordinated regulation of photosynthesis: P binds to the RuBisCO active site and to another site on the large chain where it can influence transitions between activated and less active conformations of the enzyme. In this way, activation of bacterial RuBisCO might be particularly sensitive to P levels, which might cause it to act in a similar way to how RuBisCO activase functions in higher plants.