The concept of receptor affinity does not only apply to the original receptor and ligand. For which of the following pairs of interacting molecules in signal transduction would a change in affinity of one for the other NOT affect how they work in signal transduction?
A) calmodulin / calcium
B) receptor tyrosine kinase / phosphate
C) protein kinase A / cAMP
To determine which pair of interacting molecules in signal transduction would not be affected by a change in affinity, we need to understand the concept of receptor affinity and how it relates to the functioning of these molecules in signal transduction.
Receptor affinity refers to the strength or binding capability of a receptor for its ligand. The higher the receptor affinity for a ligand, the more strongly it will bind, leading to a more potent response. In signal transduction, molecules interact with each other to transmit and amplify signals in cells.
Let's analyze the given options:
A) Calmodulin / Calcium: Calmodulin is a calcium-binding protein, and calcium is the ligand that binds to calmodulin. A change in the affinity of calmodulin for calcium would definitely affect how they work in signal transduction because the binding of calcium to calmodulin is a critical step in the activation of various downstream signaling pathways.
B) Receptor Tyrosine Kinase / Phosphate: Receptor Tyrosine Kinases (RTKs) are cell surface receptors that can be phosphorylated by adding a phosphate group. A change in the affinity of RTKs for phosphate would certainly impact their functioning in signal transduction because phosphorylation plays a crucial role in activating downstream signaling cascades.
C) Protein Kinase A / cAMP: Protein Kinase A (PKA) is an enzyme that is activated by binding to cyclic Adenosine Monophosphate (cAMP). A change in the affinity of PKA for cAMP would indeed affect the functioning of these molecules in signal transduction. The binding of cAMP to PKA is necessary for its activation and subsequent phosphorylation of downstream targets.
Based on our analysis, the only option where a change in affinity of one molecule for the other would NOT affect their functioning in signal transduction is:
C) Protein Kinase A / cAMP
In the case of Protein Kinase A and cAMP, a change in their affinity would impact their interaction but not necessarily how they work in signal transduction. However, it is important to note that the exact impact on signaling may vary based on the specific context and downstream targets involved.