What is a messenger protein?

A messenger protein, often referred to as a signaling protein, is a type of protein that transmits signals between cells or within cells to initiate various biological processes. These proteins play crucial roles in communication pathways, such as hormones and neurotransmitters, by binding to specific receptors and triggering cellular responses. They are essential for regulating functions like growth, metabolism, and immune responses. Examples include insulin, which regulates glucose levels, and cytokines, which modulate immune responses.