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
I think its c
It is B
To determine which of the following pairs of interacting molecules in signal transduction would not be affected by a change in affinity, we need to understand the role of receptor affinity in signal transduction and analyze each option:
In signal transduction, ligands bind to specific receptors, initiating a cascade of events that ultimately lead to a cellular response. Receptor affinity refers to the strength of the interaction between a ligand and its receptor.
Now let's analyze each option to see if a change in affinity would affect how they work in signal transduction:
A) Calmodulin / Calcium:
Calmodulin is a calcium-binding protein that plays a crucial role in the regulation of various cellular processes. Calcium binds to calmodulin, leading to conformational changes that enable it to interact with and activate downstream target proteins. The affinity between calmodulin and calcium is essential for this process. If there was a change in affinity, it could affect the binding efficiency and downstream signaling, thereby impacting how they work in signal transduction. Therefore, a change in affinity would affect how calmodulin and calcium work in signal transduction.
B) Receptor tyrosine kinase / Phosphate:
Receptor tyrosine kinases (RTKs) are transmembrane receptors that are activated by ligand binding. Once activated, they undergo autophosphorylation on tyrosine residues, allowing them to recruit and activate downstream signaling molecules through binding to proteins containing phosphotyrosine-binding domains. The affinity of the RTK for phosphate is crucial for proper signal transduction because it determines the strength of the interaction between the activated receptor and downstream signaling molecules. If there was a change in affinity, it could affect the binding efficiency and subsequently alter downstream signaling. Therefore, a change in affinity would affect how receptor tyrosine kinase and phosphate work in signal transduction.
C) Protein kinase A / cAMP:
Protein kinase A (PKA) is a crucial enzyme involved in many signaling pathways and is activated by the second messenger cyclic adenosine monophosphate (cAMP). PKA consists of regulatory subunits that bind to cAMP, leading to a conformational change that releases the active catalytic subunits. The affinity between PKA and cAMP is important for regulating its activity. However, if there was a change in affinity between PKA and cAMP, it would not affect how they work in signal transduction because the presence of cAMP is necessary for PKA activation. As long as there is sufficient cAMP to bind to PKA, it will activate the enzyme and initiate downstream signaling. Therefore, a change in affinity between protein kinase A and cAMP would not affect how they work in signal transduction.
Based on this analysis, the correct answer is C) protein kinase A / cAMP.