S100 Calcium Binding Protein A13, Recombinant, Human (S100A13)

S100A13 is an 11kD member of the S100 (soluble in 100% saturated ammonium sulfate) family of vertebrate EF-hand Ca ++ -binding proteins. It is widely expressed as a homodimer with two 98 amino acid (aa) long subunits. Human S100A13 shares 83%, 90%, , 91%, 87%, 78% and 47% aa identity with mouse, rat, cow, dog, opossum and chicken S100A13, respectively. Like other S100 proteins, S100A13 is small and generally acidic, but contains a basic residue-rich sequence at the C terminus, and two EF hand motifs that bind , with Ca ++ differing affinities. Some S100 proteins, including S100A13, are able to bind the cell surface receptor for advanced glycation end-products (RAGE). Despite lacking a signal sequence, S100A13 plays an important role in Cu ++ -dependent export of FGF-1 (FGF acidic) and IL-1a from the cell in response to stresses such as heat shock, anoxia and starvation. Binding of copper is necessary for formation of a multi-protein complex between S100A13, FGF-1 and p40 synaptotagmin-1 (syt-1). Cu++ ions supplied by S100A13 are thought to oxidize and downregulate the activity of FGF-1 prior to export. Calcium influx may also play a similar role in FGF-1 release from neuronal cells. S100A13 is composed of four amphiphilic helices that may interact with acidic phospholipid headgroups. With FGF-1 and syt-1, S100A13 likely perturbs the membrane, which allows the S100A13 protein complex to exit the cell. S100A13 has been proposed as a marker for angiogenesis in tumors and endometrium, due to its role in stress-induced export of FGF-1. Based on in house studies, S100A13 has also been found to promote neurite outgrowth from rat cortical embryonic neurons. Molecular Mass: The 97 amino acid residue non-methionyl form of the recombinant human S100A13 has a predicted molecular mass of approximately 11.3kD. Activity:, Measured by its ability to enhance neurite outgrowth of cortical neurons from E18 rat embryos. Immobilized rhS100A13 (at a 3il droplet containing 100 ng) on a nitrocellulose coated microplate is sufficient to significantly enhance neurite outgrowth. Storage and Stability: Lyophilized powder may be stored at -20°C. Stable for 12 months at -20°C. Reconstitute with sterile PBS, 0.1% HSA or BSA. Aliquot to avoid repeated freezing and thawing. Store at -20°C. Reconstituted product is stable for 6 months at -20°C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.