Junctional Sarcoplasmic Reticulum Protein 1 (JSRP1)

The sarcoplasmic reticulum (SR) is an intracellular membrane compartment that controls intracellular calcium concentration and therefore plays a role in excitation-contraction coupling. In mouse skeletal muscle, Jp45 interacts with key proteins involved in excitation-contraction coupling at the SR. Mouse and human JP45 share 50% amino acid identity overall and 91% identity within the transmembrane domain. Human JP45 contains 331 amino acids. Northern blot analysis detected mouse Jp45 expression only in skeletal muscle. Jp45 was expressed in the membrane fraction of mouse skeletal muscle and tongue lysates and in the membrane fraction of transfected human embryonic kidney cells. Immunofluorescence analysis of adult rat muscle fibers found Jp45 colocalized with ryanodine receptors in SR triad membranes.