Fig. 4
From: Models in biology: lessons from modeling regulation of the eukaryotic cell cycle
The regulation of protein phosphatase 2A during mitosis. a Molecular mechanism. Adapted from figure S1 of [38]. As in earlier figures, solid arrows represent chemical reactions; dashed arrows represent catalytic activities. The T-shaped connector with black dots on the crossbar and an arrowhead on the stem represents the reversible binding of two proteins to form a heterodimer. b Signal-response curve for PP2A:B55δ. Adapted from figure 5B of [38]. For a fixed activity of MPF we plot the corresponding steady state activity of PP2A:B55δ, the phosphatase that counteracts certain MPF-driven phosphorylations. The middle branch of the Z-shaped curve corresponds to unstable steady states. c Signal-response curve for APC. Figure S4 of [38]; used by permission. For a fixed activity of MPF we plot the corresponding steady state activity of APC, the ubiquitin-conjugating enzyme that labels cyclin B for degradation. Compare to panel (b)