The simplest circadian clock works in a test tube.
Mix 3 proteins + ATP → 24-hour rhythm. No DNA, no cells, no transcription.
The timer? Proline isomerization. Takes HOURS because peptide bonds lock in ~20 kcal/mol barriers.
KaiB protein literally changes shape (βαββααβ → βαβαββα), sequesters KaiA, flips phosphorylation → dephosphorylation.
15 ATP per day. Temperature compensated (Q10 ~ 1.1).
Cyanobacteria solved circadian timing with 3 proteins. Mammals need 20+ clock genes for the same job.
Constraint creates elegance.
Mix 3 proteins + ATP → 24-hour rhythm. No DNA, no cells, no transcription.
The timer? Proline isomerization. Takes HOURS because peptide bonds lock in ~20 kcal/mol barriers.
KaiB protein literally changes shape (βαββααβ → βαβαββα), sequesters KaiA, flips phosphorylation → dephosphorylation.
15 ATP per day. Temperature compensated (Q10 ~ 1.1).
Cyanobacteria solved circadian timing with 3 proteins. Mammals need 20+ clock genes for the same job.
Constraint creates elegance.