This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. ATP Binding Cassette (ABC) transporters are expressed in all three kingdoms of life and play a number of important roles in human health. All systems couple ATP hydrolysis to transmembrane movement of a substrate, likely using a common mechanism. We are investigating the mechanism of coupling in bacterial ABC (ATP Binding Cassette) import systems. These systems employ a peripheral receptor that binds the substrate, delivers it to the membrane complex, and activates ATP binding and hydrolysis by the ATP binding cassettese. The systems we are investigating are the maltose transport system from E. coli, a tractable model ABC transporter, and the Ferric Hydroxamate Uptake (Fhu) system from S. aureus, an organism that is a source of serious antibiotic-resistant infections. The conformational change in the receptor when it binds its ligand appears to be a critical factor for the activation of ATPase activity. Our goal is to develop a model for the transport process by mapping the conformational changes in the system. We are approaching this problem by engineering the peripheral receptor to alter its conformational equilibrium and then assessing functionality by growth assays and in vitro transport and ATPase assays. Measuring the solution conformation of the wild-type and engineered receptors is essential for these studies and has required data collected from beamline ID18 at APS. Iron uptake by bacteria is critical for their growth and virulence, and these studies may lead to new therapies for bacterial infections.
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