Andreea Andrei
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Functional investigation of proteins involved in copper transport
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Abstract
Cytochrome c oxidases (Cox) are universally conserved multi-subunit enzyme complexes, which terminate the respiratory chains in aerobic and facultative aerobic cells. They belong to the heme-Cu oxidase superfamily of proteins and require Cu in their catalytic centre for activity. Although the requirement for Cu is known since decades, it is largely unknown how Cu is specifically delivered and inserted into Cox. The cbb3-type Cox of the α-proteobacterium Rhodobacter capsulatus has developed into a perfect model system for analyzing this and a tangled network of proteins for uptake and delivery of Cu was identified. Based on the available data, a tentative model for Cu homeostasis was developed: Cu(II) is transported into the cytoplasm via the major facilitator superfamily protein CcoA. In the cytoplasm, Cu is either bound by the Cu chaperone CopZ or reduced to Cu(I) by the ferredoxin-like protein, CcoG. Cu(I) is then transported back into the periplasm by the P1B-type ATPase CcoI. In the periplasm, two periplasmic chaperones PccA and SenC are required for Cu insertion into the active center of CcoN, the catalytic subunit of cbb3-type Cox. Even though this model provides a first framework of the complexity of Cu insertion, many molecular details are still missing. In order to delineate this process further, the molecular details of the protein-protein interaction network and the temporal and spatial organization of the Cu insertion pathway have to be revealed.
Methods
- Membrane protein expression and purification
- Reconstitution of Cu transport processes
- 64Cu binding and transport assay
- Cox activity assay
- Site directed and chemical cross-linking
