Recently we determined the first crystal structure for the KDEL trafficking receptor, which functions to maintain the integrity of the ER and Golgi. The receptor functions by selectively retrieving ER luminal proteins, which contain a C-terminal KDEL retention signal, in a pH dependent manner from the Golgi back to the ER via COPI coated vesicles. The structure and associated functional insights reveal a remarkable and somewhat unexpected similarity to membrane transporters, which in contrast to trafficking receptors, function to shuttle nutrients and small molecules across a single membrane rather than between two separate membrane environments. In this talk I will present how these insights uniquely bring together what where once considered two different themes of cell biology, transport and trafficking, and discuss how these two systems share mechanisms for peptide recognition and proton coupling in the cell.