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Syntaxin N-terminus domain; syntaxins are nervous system-specific proteins implicated in the docking of synaptic vesicles with the presynaptic plasma membrane; they are a family of receptors for intracellular transport vesicles; each target membrane may be identified by a specific member of the syntaxin family; syntaxins contain a moderately well conserved amino-terminal domain, called Habc, whose structure is an antiparallel three-helix bundle; a linker of about 30 amino acids connects this to the carboxy-terminal region, designated H3 (t_SNARE), of the syntaxin cytoplasmic domain; the highly conserved H3 region forms a single, long alpha-helix when it is part of the core SNARE complex and anchors the protein on the cytoplasmic surface of cellular membranes; H3 is not included in defining this domain