Orderly wheels of the cyanobacterial clock

Circadian rhythms, self-sustaining oscillations in an organism’s behavior that repeat roughly once per day, have fascinated biologists for hundreds of years (1, 2). Part of this fascination comes from the fact that the existence of intrinsic biological rhythms implies that an organism carries within it a model of how it expects the external world to behave—a plant that moves its leaves in anticipation of the sun even when grown in constant conditions must have some hard-wired knowledge of the rotation of the Earth. Fundamentally, these predictive biological rhythms must originate mechanistically from carefully regulated molecular interactions that generate oscillations. In PNAS, Chang et al. (3) present a series of cleverly designed structural and biochemical experiments that shed light on the inner workings of the best-defined biological clock, the KaiABC protein oscillator.

Commentary on:  Chang Y-G, Tseng R, Kuo N-W, LiWang A (2012) Rhythmic ring–ring stacking drives the circadian oscillator clockwise. Proc Natl Acad Sci USA, 10.1073/pnas.1211508109 (http://www.pnas.org/content/109/42/16847.long)