Saporin is obtained from the seeds of the Soapwort plant (Saponaria officinalis), a plant that grows wildly in Britain and other parts of Europe. Saporin is a plant enzyme with N-glycosidase activity that depurinates a specific nucleotide in the ribosomal RNA 28S, thus irreversibly blocking protein synthesis. It belongs to the well-characterized family of ribosome-inactivating proteins (RIPs). There are two types of RIPs: type I, which are much less cytotoxic due to the lack of the B chain and type II, which are distinguished from type I RIPs by the presence of the B chain and their ability to enter cells on their own. However, type I RIPs can still be internalized by fluid-phase endocytosis. In the case of saporin, it was reported that saporin first binds to the alpha2-macroglobulin receptor on human cells and is then internalized to the cytosol. Upon internalization, the ribosomes are inactivated, resulting in cell death.
Saporin (molecular weight 30 kDa) has no known specificity. Saporin is purified from the seeds of the Soapwort plant (Saponaria officinalis) and is then routinely tested for activity by a protein synthesis inhibition assay. Saporin is labeled with biotin in a 1:1 chemically-determined average molar ratio.
Saporin serves as a control for targeted saporin immunotoxins or ligand toxins. MonoBiotin-ZAP uses your streptavidinylated targeting agent to target and eliminate cells. This secondary conjugate is used to evaluate the potential of a streptavidinylated targeting agent to internalize.
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