Proteins A-E constitute a pathway that signals for cell growth. In different exp

Question

Proteins A-E constitute a pathway that signals for cell growth. In different experiments, you activate each protein using different drugs, and you observe whether cells grow. In the following pathway, please draw in activating (rightarrow) and inhibiting arrows (-1) to connect proteins A-E to be consistent with your findings. Pathway: A B C D E Cell Growth The following lists molecules involved in the fight-or-flight signaling response. Please describe how proteins or other mechanisms in wild-type cells "turn off" the following proteins and second messengers after they have been activated. GPCR (adrenergic receptor)- G-protein alpha (G_as)- Adenylyl cyclase - cAMP- Glycogen phosphorylase- B. In Part A, circle which one(s) need to be "turned off" for the signaling response to be stopped.

Explanation / Answer

3A. G-protein-coupled receptors (GPCRs) are the largest and most diverse group of membrane receptors in eukaryotes. These cell surface receptors act like an inbox for messages in the form of light energy, peptides, lipids, sugars, and proteins.

G protein alpha subunit binds either GTP or GDP depending on whether the protein is active (GTP) or inactive (GDP). In the absence of a signal, GDP attaches to the alpha subunit, and the entire G protein-GDP complex binds to a nearby GPCR. This arrangement persists until a signalling molecule joins with the GPCR. At this point, a change in the conformation of the GPCR activates the G protein, and GTP physically replaces the GDP bound to the alpha subunit.

The first class of adenylyl cyclases occur in many bacteria including E. coli. This was the first class of AC to be characterized. It was observed that E. coli deprived of glucose produce cAMP that serves as an internal signal to activate expression of genes for importing and metabolizing other sugars. cAMP exerts this effect by binding the transcription factor CRP also known as CAP.

Glycogen phosphorylase has a pyridoxal phosphate (PLP, derived from Vitamin B6) at each catalytic site. Pyridoxal phosphate links with basic residues (in this case Lys680) and covalently forms a Schiff base.

Related Questions

Navigate

• Browse (All)
• Browse P
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.