SAG Antibody – Mouse Monoclonal

Monoclonal

IgG1

Mouse

Human, bovine, mouse, pig and rat

Liquid

Affinity purified

100ug/100ul (lot specific)

Store at -20 degree C/1 year

The arrestin proteins are a family of regulators of cell signaling of G protein-coupled receptors (GPCR). Visual arrestin was first discovered as a result of the experimental model of human uveitis, an autoimmune disease of the eye. In this model, called experimental allergic uveitis, animals were injected with extracts made from the retina of the same species mixed with Freund's complete adjuvant. The animals mounted a strong immune response to the extract, and the antibody response was used to identify several immunogenic retinal proteins. One of these was called S-antigen, for soluble antigen. The protein was found to be abundant in retina, about 48kDa in molecular weight, and localized in the outer segments of the photoreceptors (1, 2). Several years later, Hermann Kühn and colleagues discovered that this protein binds to phosphorylated rhodopsin and prevents this protein from activating transducin (3, 4, 5). Transducin is a typical heterotrimeric G protein, composed of α and betagamma subunits. Rhodopsin phosphorylation is mediated by Rhodopsin kinase (a.k.a. GRK1), the prototypic member of a family of GPCR kinases. Since the S-antigen protein arrested the activity of rhodopsin it was renamed arrestin, and became the prototypic member of the arrestin protein family. Subsequently, Robert Lefkowitz and colleagues discovered a related protein which bound to phosphorylated beta-adrenergic GPCRs and prevented these proteins from activating their specific heterotrimeric G proteins (6). Because of this relationship to the beta-adrenergic receptor and functional and structural similarities to visual arrestin this protein was named beta-arrestin. The beta-adrenergic receptor was phosphorylated by the beta-adrenergic receptor kinase (a.k.a. GRK2), an enzyme belonging to GPCR kinase family. Studies of visual transduction therefore aided greatly in understanding other kinds of GPCR signaling. In mammals, there are four arrestin isoforms; Visual arrestin (a.k.a. S-antigen and arrestin-1) and cone arrestin (a.k.a. arrestin-4) are largely confined to photoreceptors. beta-arrestin 1 (a.k.a. arrestin 2) and beta-arrestin-2 (a.k.a. arrestin-3) are ubiquitous and regulate non-visual GPCRs. MCA-S128 was raised against recombinant bovine arrestin-1 with the first 20 amino acids of the C-terminus truncated. The antibody does not bind the other three arrestin molecules. In the retina MCA-S128 binds to rod cell bodies and rod outer seqments. The HGNC name for this protein is SAG.

PBS, pH 7.4 with 0.02% sodium azide.