Fig. 1

Reaction diagrams for the cyanobacterial clock models. Reaction diagrams for the detailed model (A), core model (B), TTFL model (C), and the PTR model (D). A Squares are proteins in various states; small circles indicate the phosphatase groups on the corresponding sites (red corresponds to the T432 site and yellow to the S431 site). Arrows indicate reactions among proteins, the width of which shows the relative strength. B The schematic of the core mechanism where KaiA enhances only the phosphorylation from U to T. C Extension of the core mechanism: the TTFL as an inhibition scheme where KaiC-S acts like an inhibitor of the kaiBC gene. D Schematic of the post-translational regulation (PTR) model with a constitutive source of transcription