SYNTAXIN-12, A MEMBER OF THE SYNTAXIN FAMILY LOCALIZED TO THE ENDOSOME

We have cloned a new member of the syntaxin family of proteins, The op en reading frame encodes a polypeptide of 272 amino acids with potenti al coiled-coil domains and a C-terminal hydrophobic tail, Northern blo t analysis showed that the transcript is fairly ubiquitous, A soluble recombinant form of the polypeptide without the hydrophobic region bin ds to alpha-SNAP (soluble N ethylmaleimide-sensitive factor attachment protein) and syndet/SNAP-23 in vitro, Polyclonal antibody raised agai nst the recombinant protein recognized a 39-kDa protein in the membran e fraction of cell lysates, Indirect immunofluorescence studies using the polyclonal antibody showed that the protein is localized to intrac ellular membrane structures, Selective permeabilization studies with d igitonin and saponin indicate that the epitope(s) recognized by the an tibody is expose to the cytoplasm, consistent with the predicted orien tation characteristic of SNAP receptor molecules, Morphological altera tions of the staining pattern of the protein with brefeldin A and wort mannin treatment indicate that the protein is localize to the endosome , The cDNA we have cloned apparently corresponded to three previously described expressed sequence tags named as syntaxins 12, 13, and 14, r espectively, We therefore propose to retain the name syntaxin 12 for t his protein.