Real-time NMR of a Circadian Clock
Dr. Archana Chavan
All living organisms have evolved to respond the day and night cycle through the system called circadian clocks. Animals use these circadian clocks to regulate healthy cycles of activity and rest in anticipation of sunrise and sunset. Like gears of a mechanical clock, the clock proteins keep time by interacting with one another. Despite their importance to life on Earth, molecular mechanisms of biological clocks remain mysterious, and face two major challenges: (1) gears of biological clock are tiny proteins that needs to be observed at atomic resolution, and (2) as these protein gears are constantly moving in synchronized interplay, real-time measurements of their states are crucial for elucidation of molecular mechanism. While several atomic-resolution structures of circadian clock proteins are available, they represent only a few frozen states within crystals. And, real-time measurements have been at resolutions that are too low to see how clock proteins move to tell time. We developed an approach using nuclear magnetic resonance (NMR) spectroscopy that can observe in real time and at atomic resolution a fully reassembled and functional circadian clock as it ticks over many days in a test tube. These experiments are expected to reveal how and when residues of clock proteins move to tell time.