ATP7B (Wilson disease protein) is a human copper transporter powered by ATP hydrolysis. ATP7B delivers copper to some proteins that use it as a cofactor, and also removes excess copper from the cell in a complex process that involves copper translocation across the lipid membrane and fusion of membrane vesicles with the plasma membrane. Activity of ATP7B is regulated by copper binding to six small and highly mobile cytosolic metal-binding domains, which are connected by flexible linkers. We use protein NMR spectroscopy to study how dynamics and interactions of the metal-binding domains signal activation of copper transport and direct ATP7B localization in the cell.
Cisplatin, carboplatin and oxaliplatin are platinum derivatives that are widely used to treat several common types of cancer. Cancer cells often develop resistance to platinum drugs and that undermines effectiveness of chemotherapy. We are investigating the role that copper transport proteins Atox1 and ATP7B play in cancer resistance to cisplatin and similar drugs. Our work has uncovered remarkable parallels between the pathways of copper and platinum transport in the cell. Manipulating these pathways in cancer cells may increase effectiveness, and reduce toxicity of platinum anticancer drugs.
Bacterial multidrug resistance proteins can pump an amazingly wide range of toxic chemicals out of the cell. This is in contrast to most other membrane transport proteins, which are quite selective in their substrates. Physiological role of multidrug resistance proteins and the mechanism underlying their substrate promiscuity are still, to a large extent, a mystery. We are particularly interested in the proteins belonging to the major facilitator superfamily, a large and functionally diverse group of membrane transporters, which use the energy of ion gradients to pump substrates across the cell membrane. We study transport mechanism of an E. coli multidrug resistance protein MdfA using NMR spectroscopy and model systems, where drug transport can be reconstituted with purified protein incorporated into the artificial lipid vesicles.