Skip to main content
. Author manuscript; available in PMC: 2016 May 1.
Published in final edited form as: Bull Math Biol. 2014 Sep 4;77(5):796–816. doi: 10.1007/s11538-014-0009-9

Figure 8. MPF oscillations in cycling extracts.

Figure 8

Data from Pomerening et al. (2005); used by permission. Frog egg cytoplasmic extracts are prepared without addition of either cycloheximide or exogenous non-degradable cyclin B. The extract synthesizes endogenous degradable cyclin B from maternal mRNA. Such extracts can exhibit three or more spontaneous cycles of MPF activation and inactivation. (A) Careful measurements of total cyclin concentration and MPF activity during the first mitotic cycle. (B) Replotting the data in panel A on the phase plane, MPF activity versus total cyclin concentration, parameterized by time (increasing in direction of arrows). The oscillation follows the hysteresis loop predicted in Fig. 4B. (C) MPF oscillations in cycling extracts supplemented with 200 nM Cdc2 protein that is phosphorylable (Cdc2wt, left) or non-phosphorylable (Cdc2AF, right). The Cdc2wt extract exhibits relaxation oscillations (spikes of MPF activation). As predicted by the model, oscillations in the Cdc2AF extract (with compromised positive feedback loops) are more sinusoidal, more rapid, and of lower amplitude.