SLC6A19, also known as B0AT1, is a member of the Na+ -dependent neurotransmitter transporter family, and mediates epithelial resorption of neutral amino acids across the apical membrane in the intestine and the proximal tubes of the renal cortex. Defective amino acid transport due to the mutation of the SLC6A19 gene causes Hartnup disorder, which is characterized by a pellagra-like light-sensitive rash, cerebellar ataxia, emotional instability, and aminoaciduria.