VIAAT (Vesicular inhibitory aa transporter; also VGAT and SLC32A1) is a 56-58kD member of the aa/polyamine transporter 2 family of proteins. It is expressed in inhibitory neurons throughout the CNS, in both resting and activated lymphocytes, and in pancreatic acells (in rodent). VIAAT is believed to transport both GABA and glycine across synaptic vesicle membranes in an electrical and pH gradient dependent manner. Once transported, these neurotransmitters are released at the presynaptic membrane, acting as inhibitory factors in the mature nervous system, and excitatory factors in the immature nervous system. Human VIAAT is a 525aa 10-transmembrane nonglycosylated protein. The N-terminus (aa1-133) and C-terminus (aa511-525) are cytoplasmic. There is a 52kD short form that is not well characterized. Over aa2-133, human VIAAT shares 95% aa identity with mouse VIAAT.