Calsequestrin

Calsequestrin is a calcium-binding protein or 'buffer' that is found within the sarcoplasmic reticulum (SR) of muscle cells. Calsequestrin binds calcium ions with relatively low affinity, this allows calcium ions to flow without much resistance out of the sarcoplasmic reticulum and into the intracellular environment when the SR is stimulated at ryanodine receptors (RyR's) by calcium. This is unlike calcium sensors ( such as calmodulin) that bind calcium ions with a higher affinity.