What is an example of a protein receptor that can initiate a signal transduction cascade?

An example of a protein receptor that can initiate a signal transduction cascade is the cellular response to insulin. Insulin receptors are part of a larger category of protein receptors known as receptor tyrosine kinases. When insulin binds to its receptor on the surface of a cell, it activates the receptor's intrinsic kinase activity, leading to phosphorylation of tyrosine residues on specific target proteins. This phosphorylation triggers a cascade of downstream signaling pathways that ultimately result in various cellular responses, such as the uptake of glucose into cells and modulation of metabolic processes.

This process highlights the role of signal transduction in cell communication and the regulation of physiological functions. It demonstrates how extracellular signals, like hormones, can lead to profound cellular responses through intricate signaling pathways, exemplifying the efficiency of protein receptors in mediating biological responses.