In humans, there are more than 50 types of amino acid transporters, which are responsible for the cellular uptake of amino acids and for regulating the intra- and extra-cellular balance of these molecules. Mutations in these transporters are associated with a variety of diseases. However, in spite of the importance of these molecules, little is known about how they work. Scientists at the Institute for Research in Biomedicine (IRB Barcelona) have now characterised the structure of a member of the LAT family.