Calcium-binding proteins are specialized proteins that can bind calcium ions, playing crucial roles in various biological processes. They help regulate cellular functions such as muscle contraction, neurotransmitter release, and cell signaling. These proteins often undergo conformational changes upon binding calcium, which allows them to interact with other molecules and influence cellular activities. Examples of calcium-binding proteins include calmodulin, which is involved in many signaling pathways, and troponin, which plays a key role in muscle contraction. The ability to bind calcium makes these proteins essential for maintaining proper physiological functions in living organisms.