PERIOD–TIMELESS Interval Timer May Require an Additional Feedback Loop

Figure 2

Models of the Isolated per/tim Loop

(A) The simple mass action kinetics model.

(B) The serial model is based on a series of intermediate (possibly phosphorylated) PER–TIM states.

(C) The feedback model proposes a new role for PER providing positive feedback on the dissociation of cytoplasmic PER–TIM complexes.