Calsequestrin is a calcium-binding protein primarily found in the sarcoplasmic reticulum of muscle cells. Its main function is to store calcium ions, which are crucial for muscle contraction. By regulating calcium levels, calsequestrin helps ensure that calcium is available for release during muscle activation and is also involved in the reuptake of calcium after contraction, thus playing a key role in muscle relaxation.
Calsequestrin is primarily associated with cardiac and skeletal muscle fibers, where it plays a critical role in calcium storage within the sarcoplasmic reticulum. It is particularly relevant in fast-twitch fibers, which require rapid calcium release for quick and powerful contractions. Calsequestrin helps regulate calcium levels during muscle contraction and relaxation, contributing to muscle efficiency and performance.
Striated muscles, like all other muscles, including cardiac and smooth, use a method called the sliding filament theory. This is the current model of how muscles contract and was developed by Hugh Huxley in the 1960's.