Using Thermodynamics to Reveal the Mechanisms behind the Robust Ticking, Input Compensation and Entrainability of the Cyanobacterial Circadian Clock
Event details
| Date | 10.04.2017 |
| Hour | 14:00 |
| Speaker | Joris Paijmans, Ph.D., AMOLF, Amsterdam (NL) |
| Location | |
| Category | Conferences - Seminars |
BIOENGINEERING SEMINAR
Abstract:
The circadian clock of the cyanobacterium S. elongatus, called the Kai oscillator, is one of the best studied and simplest found in biology. Remarkably, the three clock proteins KaiA, KaiB, and KaiC, together with ATP, are sufficient to generate circadian phosphorylation of KaiC in a test tube. How this clock is driven thermodynamically is still not well understood. In this talk I present our new mathematical model of the in-vitro Kai system which simulates detailed dynamics of KaiC homohexamers as they traverse their phosphorylation cycle. Because all reactions uphold detailed balance, we can precisely study how hydrolysis of ATP makes the clock tick. We then use this model to study another intriguing problem. All circadian clocks must be able to entrain to time-varying signals to keep their oscillations in phase with the day-night rhythm. On the other hand, they must also exhibit input compensation: their period must remain about one day in different constant environments. The Kai system can be entrained by transient or oscillatory changes in the ATP fraction, yet is insensitive to constant changes in this fraction. We show how, by a new mechanism at the level of individual hexamers, the Kai system can meet these seemingly contradictory requirements.
Bio:
2012–present
PhD Researcher in Biophysics
FOM Institute AMOLF, Amsterdam
2006 – 2011:
Bsc Natuur en Sterrenkunde
MSc Theoretical Physics
University of Amsterdam
Abstract:
The circadian clock of the cyanobacterium S. elongatus, called the Kai oscillator, is one of the best studied and simplest found in biology. Remarkably, the three clock proteins KaiA, KaiB, and KaiC, together with ATP, are sufficient to generate circadian phosphorylation of KaiC in a test tube. How this clock is driven thermodynamically is still not well understood. In this talk I present our new mathematical model of the in-vitro Kai system which simulates detailed dynamics of KaiC homohexamers as they traverse their phosphorylation cycle. Because all reactions uphold detailed balance, we can precisely study how hydrolysis of ATP makes the clock tick. We then use this model to study another intriguing problem. All circadian clocks must be able to entrain to time-varying signals to keep their oscillations in phase with the day-night rhythm. On the other hand, they must also exhibit input compensation: their period must remain about one day in different constant environments. The Kai system can be entrained by transient or oscillatory changes in the ATP fraction, yet is insensitive to constant changes in this fraction. We show how, by a new mechanism at the level of individual hexamers, the Kai system can meet these seemingly contradictory requirements.
Bio:
2012–present
PhD Researcher in Biophysics
FOM Institute AMOLF, Amsterdam
2006 – 2011:
Bsc Natuur en Sterrenkunde
MSc Theoretical Physics
University of Amsterdam
Practical information
- Informed public
- Free