The proteins that belong to the HAT family are essential for life as they transport amino acids across the cell membrane. Although the members of this family are practically identical, some transport certain amino acids and not others. This specialization determines their involvement in specific functions, such as cell growth or neuronal functions, and consequently in related diseases like cancer or neurodegenerative conditions such as Alzheimer´s disease. What confers this specificity and diversity of functions? This is one of the questions asked by researchers at the Spanish National Cancer Research Center (CNIO) and the Institute for Research in Biomedicine (IRB Barcelona), who led the study, and one whose answer has been published this week in the journal Proceedings of the National Academy of Sciences (PNAS).