Molecular Mechanism of Regulation of the Human Copper Transporter ATP7B

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Copper is an essential cofactor in many biological processes, yet excess of copper is highly toxic for the cells, and acquisition, distribution and removal of copper from the human cells is tightly controlled. Copper transport processes in the cell are complex and not well understood at present. The long term goal of our research is to elucidate the molecular mechanism of copper transport in human tissues. The key enzymes in copper metabolism in the cell are two structurally similar ATP-driven membrane transporters, ATP7B, which is the focus of this research proposal, and ATP7A. Enzymatic activity and intracellular localization of ATP7B are regulated by copper. In the cell, copper, delivered by a chaperone protein Atox1, is transferred to the chain of six cytosolic metal binding domains (MBD1-6) of ATP7B. Conformation of MBD1-6, the subsequent steps of intramolecular copper transfer, and the mechanism of ATP7B regulation by copper are unknown. Our central hypothesis is that copper-dependent changes in the interactions and the three-dimensional fold of the MBD chain trigger relocalization of ATP7B from the trans-Golgi network to the cytosolic membrane vesicles and plasma membrane, and activate copper transport across the cell membranes and out of the cell. Using high-resolution NMR, small-angle X-ray scattering (SAXS) and biochemical methods, we will determine how the conformation and dynamics of MBD1-6 regulate activity and intracellular localization of MBD1-6. This work will provide new insight into the fundamental principles of biological regulation of multidomain eukaryotic proteins, and advance our knowledge of metal transport processes in the human cells.