Secondary active transporters form one of the most versatile and abundant class of membrane proteins. They transport all kinds of substrates across biological membranes. For this reason, they form the major focus of this collaborative research center. The aim of the research is to contribute to an understanding of the molecular mechanisms of these transporters at the atomic level. This means that their atomic structures have to be known before the full power of genetic, spectroscopic, and computational techniques can be brought to bear on them. Work in CRC 807 has been highly successful in this respect as documented by the substantial number of publications in high-ranking journals.