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Cyanobacterial Oscillator The little oscillator that could... Hetmann Hsieh Jeff Lau Dave Ramos Zhipeng Sun Harvard iGEM 2006 Cyanobacterial Oscillator Harvard iGEM 2006 The Kai Clock in Cyanobacteria Three proteins-- KaiA, KaiB, and KaiC– interact to produce oscillation in the phosphorylation state of KaiC. • Reconstituted in vitro with Kai genes (Nakajima et al., 2005) • Oscillation does not require transcriptional regulation P • Desirable properties: • Stable over time P • Temperature compensated • Period can be adjusted via P mutations in Kai genes (reference?) P P P Tomita et al, 2005 Cyanobacterial Oscillator Harvard iGEM 2006 Project Goals Reconstitute the cyanobacteria Kai oscillator in E. coli 1. Create KaiA, KaiB, and KaiC BioBricks. 2. Combine the above with promoters, etc. to form functional BioBricks. 3. Express Kai proteins in E. coli and verify interaction. 4. Verify oscillation in E. coli. Cyanobacterial Oscillator Harvard iGEM 2006 Experimental Overview • We measured the phosphorylation state of KaiC using Western blots – Problem: synchronization – Solution: pulsed expression of Kai genes • Two-stage experimental design: – Interaction (unsynchronized) – Oscillation (synchronized) Cyanobacterial Oscillator Harvard iGEM 2006 Interaction Experiments According to Tomita et al.’s model of the Kai clock: •KaiA promotes KaiC’s autophosphorylation •KaiB inhibits KaiA Experiments with constant (unsynchronized) expression of Kai genes: Kai gene combination Expected phosphorylation of KaiC KaiC low KaiB + KaiC low KaiA + KaiC high KaiA + KaiB + KaiC moderate Cyanobacterial Oscillator Harvard iGEM 2006 Results We’ve made the following constructs: Cyanobacterial Oscillator Harvard iGEM 2006 Results Western blot results (interaction experiment) Anti-KaiC antibodies Cyanobacterial Oscillator Harvard iGEM 2006 Future: Oscillation Experiments • Induce expression of Kai genes simultaneously for all cells in a culture • Take samples at regular intervals Pulse KaiA, KaiB, and KaiC expression Expect: weakening oscillation Time Constant KaiA, pulse KaiB and KaiC Expect: oscillation weakens more slowly than above; period should not change Cyanobacterial Oscillator Harvard iGEM 2006 Acknowledgements • Our TFs Chris Doucette, Shawn Douglas, and Nick Stroustrup for their valuable help in lab • Profs. Alain Viel, George Church, Pam Silver, William Shih, Radhika Nagpal, and Jagesh Shah • Prof. Susan Golden at TAMU for providing Western blot antibodies and advice • Peter Wiegele @ MIT and Eric Webb @ WHOI for cyanobacteria strains Cyanobacterial Oscillator Harvard iGEM 2006