Figure 2. AMPK phosphorylation motifs in clock proteins.

Several proteins that are critical for the functioning of mammalian circadian clocks contain evolutionarily conserved sequences that may be preferentially phosphorylated by AMPK. Intriguingly, the AMPK-dependent phosporylation of cryptochromes seems to represent an evolutionary switch in which cryptochromes gained the ability to sense changes in chemical energy (ATP levels) rather than electromagnetic energy (light).