Ca2+-calmodulin

Ca²⁺-calmodulin is a protein complex that acts as a key messenger inside cells. When calcium ions (Ca²⁺) enter a cell, they bind to a protein called calmodulin, changing its shape. This activated calmodulin then interacts with other proteins to regulate various cell activities, such as muscle contraction, nerve signaling, and gene expression. Essentially, Ca²⁺-calmodulin helps cells sense and respond to changes in calcium levels, linking external signals to internal responses that keep the cell functioning properly.