Final answer:
The control group in Experiment 2 should contain B. PKA and GSK-3 with ATP but no CREB327WT to assess the baseline autophosphorylation activity. This helps account for any activity that is not due to the substrate, CREB327WT. Answer B) is the correct choice.
Step-by-step explanation:
In Experiment 2, the control group should most likely contain PKA and GSK-3 with ATP but no CREB327WT. This control is vital for assessing the baseline autophosphorylation activity of both Protein Kinase A (PKA) and Glycogen Synthase Kinase-3 (GSK-3) in the absence of their substrate, which in this scenario is CREB327WT. By including the enzymes PKA and GSK-3 along with ATP in the control group, researchers can measure the extent of autophosphorylation that occurs without the added variable of the substrate protein. Therefore, the correct answer is B) PKA and GSK-3 with ATP but no CREB327WT.
Two possible explanations for an increase in phosphorylated ERK in cancer cells without EGF presence include constitutive activation of upstream kinases such as a mutant form of B-Raf or Ras proteins, which can phosphorylate and activate ERK without the need for EGF stimulation. Another explanation could be the presence of autocrine signaling, where the cancer cells themselves produce EGF or a similar growth factor that activates the ERK pathway.