Syntaxin Binding Protein 3 (STXBP3)

The deduced 592-amino acid protein has a calculated molecular mass of 68 kD and contains sequence motifs for protein kinase C (PKC) and casein kinase II phosphorylation. STXBP3 was predicted to be a hydrophilic protein. Northern blot analysis detected a STXBP3 transcript of about 2.7 kb in 3 megakaryocytic cell lines. Western blot analysis detected a 68-kD protein in platelet detergent extracts. STXBP3 partitioned with the cytosolic platelet fraction, with small amounts in the particulate or membrane fraction.The deduced 592-amino acid protein lacks hydrophobic sequences, suggesting that it is an intracellular cytosolic protein. Human and mouse STXBP3 share 91% amino acid identity. Northern blot analysis of mouse tissues detected a 2.8-kb transcript in all tissues examined.