SLC6A19 is a gene that provides instructions for making a protein involved in the transport of certain amino acids, particularly tryptophan, across cell membranes. This protein is primarily found in the intestines and kidneys, where it plays a crucial role in absorbing nutrients from food and maintaining amino acid balance in the body. Mutations in the SLC6A19 gene can lead to a condition known as Hartnup disorder, which affects the body's ability to absorb specific amino acids. This can result in symptoms such as skin rashes, neurological issues, and other health problems due to amino acid deficiencies.