Protein-protein interactions and conformational changes of an ATP-binding-cassette (ABC) transporter: the maltose transport system of Salmonella typhimurium III

The family of ABC transport systems comprises a diverse class of transport proteins that couple the translocation of solutes across biological membranes to the free energy of ATP hydrolysis. Members of the family exist in organisms belonging to each of the three major kingdoms of life, some of them with medical relevance. Typically, an ABC transporter consists of two membrane-spanning domains that constitute a translocation pore and of two ATP-hydrolyzing (ABC) domains. Although crystal structures of two complete transporters and of several ABC domains are available, the molecular mechanism by which these proteins exert their functions is still poorly understood. In particular, how the power stroke provided by ATP binding is signaled to the transmembrane domains to subsequently allow translocation of the substrate needs to be unraveled. Based on our findings in the previous funding period using the binding protein-dependent maltose ABC transporter of Salmonella typhimurium (MalE-FGK2) as a model system, we propose to extend our efforts to elucidate structural changes of the subunits during the transport cycle by fluorescence and EPR spectroscopy. The solution structure of a large periplasmic loop will be solved by NMR. Furthermore, we will continue to define sites of protein-protein interactions between the subunits, and with the regulatory protein enzyme IIAGlc.