Scientists reconstructed the physical evolution of a biological clock protein across 3 billion years of history.
April 1, 2026
Original Paper
Molecular Shape Evolution of Cyanobacterial Circadian Clock Protein KaiC
bioRxiv · 10.64898/2026.04.01.715469
The Takeaway
By tracking the 'molecular shape' of a vital clock protein, researchers showed how it evolved from a primitive, lopsided ring into the perfect, symmetrical gears of life we see today. The study reveals it took a billion years of physical refinement for the first self-sustained biological rhythms to emerge on Earth.
From the abstract
A primitive form of clock protein KaiC has diverged into autonomous or passive time-measuring system in prokaryotes under selective pressures of day-night environmental changes caused by the rotation of Earth. However, the timing of such functional diversification and its structural basis remain unknown. Here we traced molecular shape evolution of older KaiCs by using X-ray solution scattering and structure prediction techniques. The result shows that the oldest ancestral KaiC emerged approximat