| Syntaxin 4 (STX4) is a widely expressed type IV transmembrane protein that is a member of the syntaxin family of tSNARE (targetSoluble NSF [Nethylmaleimidesensitive factor] Attachment REceptor) membrane fusion proteins (1, 2). For membrane fusion, VAMPs (VesicleAssociated Membrane Proteins, also called Synaptotagmins) as vSNAREs on donor (vesicle) membranes interact with tSNAREs and SNAPs (Soluble NSF Attachment Proteins) on target (cell surface) membranes, with SM (Sec1/Munc18like) accessory proteins acting as catalysts for fusion (2). Human Syntaxin 4 cDNA encodes 297 amino acids (aa) including basolateral targeting motif for epithelial cells (aa2429), a coiledcoil domain termed Habc (aa43163), an Snitrosylation site which regulates fusion (aa141), a hinge region, a tSNARE domain (aa 200262), and a Cterminal transmembrane domain (aa276296) (14). Within aa1183, human Syntaxin 4 shares 89% aa sequence homology with mouse and rat, and 9495% with canine, bovine, equine, porcine, feline and ovine Syntaxin 4. Among its known roles, Syntaxin 4 and SNAP23 or SNAP25 associate with VAMP2 for fusion of GLUT4containing vesicles with the plasma membrane in muscle and adipose cells (1, 5). It is required for exocytosis of insulin from pancreatic betacells (3, 6, 7). With SNAP23 and VAMP3, it allows endosome recycling to extend podosomes during macrophage migration (79). It establishes polarization of epithelial cells, specifying basolateral sorting of proteins (4, 10). It mediates postsynaptic activitydependent exocytosis in neural cell dendritic spines (11). It is involved in exocytosis of ANP from cardiomyocytes (12). In FASmediated apoptosis, it allows translocation of acid sphingomyelinase to the cell surface (13). Syntaxin 4 binds Factin and gelsolin, linking the plasma membrane with, or releasing it from, the actin cytoskeleton (6, 7). Source: Recombinant protein corresponding to aa1-183 from human Syntaxin 4, fused to 6-his tag at C-terminal, expressed in E. coli. Molecular Weight: ~23kD Endotoxin: <0.01EU/1ug (LAL method) Storage and Stability: Lyophilized powder may be stored at -20C. Stable for 12 months at -20C. Reconstitute in sterile PBS. Aliquot to avoid repeated freezing and thawing. Store at -20C. Reconstituted product is stable for 12 months at -20C. 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. |
