Response to Comment on “‘Load-Induced Modulation of Signal Transduction Networks’: Reconciling Ultrasensitivity with Bifunctionality?”

PENG JIANG; ALEJANDRA C VENTURA; EDUARDO D SONTAG; SOFIA D MERAJVER; ALEXANDER J NINFA; DOMITILLA DEL VECCHIO

SCIENCE SIGNALING

AMER ASSOC ADVANCEMENT SCIENCE

Lugar: Washington DC; Año: 2012 vol. 5 p. 1 - 2

1937-9145

Straube suggests that a model that refl ects the bifunctional nature of the cycle enzymeuridylyltransferase/uridylyl-removing enzyme (UTase/UR) should be used, inwhich the UT and UR activities are distinct and reciprocally regulated activity statesof the enzyme, and notes that if such a model is used, the effects of retroactivityat intermediate stimulation will be different. However, such a model does not accuratelymatch the observed enzyme regulatory properties and fails to predict theultrasensitive response obtained in the experiments. Here, we argue that modelingthe UTase/UR enzyme as a bifunctional enzyme with reciprocally regulated activitystates misses important aspects of the system.