Sr-2 reacts with cardiotin, a mitochondrion-associated protein, which is present in cardiomyocytes and skeletal muscle. Sr-2 reacts with cardiomyocytes, skeletal muscle, stromal and epithelial cells as well in vivo as in vitro.
In immunoblotting assays SR-2 reacts with the 300 kDa cardiotin protein complex and its 100 kDa and 60 kDa subunits.
The antibody may be stored at 4°C. For prolonged storage prepare appropriate aliquots and store at or below -20°C. Prior to use, an aliquot is thawed slowly in the dark at ambient temperature, spun down again and used to prepare working dilutions by adding sterile phosphate buffered saline (PBS, pH 7.2). Repeated thawing and freezing should be avoided. Working dilutions should be stored at 4°C, not refrozen, and preferably used the same day. If a slight precipitation occurs upon storage, this should be removed by centrifugation. It will not affect the performance or the concentration of the product.
Cardiotin is a recently discovered, high molecular weight protein complex (~300 kDa) located in the longitudinal SR of cardiomyocytes. The cardiotin complex exists as 60 kDa and 100 kDa subunits. Both subunits contain the same amino-terminal 14 amino-acid sequence, and show high homology to human skeletal muscle alpha-actin. The tetrameric configuration of the cardiotin protein complex suggests that it exists as a transmembrane complex with the N-terminus at the cytoplasmic side of the membrane, able to interact with actin. Immunofluorescence studies colocalize cardiotin with SERCA 2a ATPase in the longitudinal sarcoplasmic reticulum (SR), although cardiotin is not expressed in junctional SR with SERCA 2.
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