Abstract
PcoC is a soluble periplasmic protein encoded by the plasmid-born pco copper resistance operon of Escherichia coli. Like PcoA, a multicopper oxidase encoded in the same locus and its chromosomal homolog CueO, PcoC contains unusual methionine rich sequences. Although essential for copper resistance, the functions of PcoC, PcoA, and their conserved methionine-rich sequences are not known. Similar methionine motifs observed in eukaryotic copper transporters have been proposed to bind copper, but there are no precedents for such metal binding sites in structurally characterized proteins. The high-resolution structures of apo PcoC, determined for both the native and selenomethionine-containing proteins, reveal a seven-stranded β barrel with the methionines unexpectedly housed on a solvent-exposed loop. Several potential metal-binding sites can be discerned by comparing the structures to spectroscopic data reported for copper-loaded PcoC. In the native structure, the methionine loop interacts with the same loop on a second molecule in the asymmetric unit. In the selenomethionine structure, the methionine loops are more exposed, forming hydrophobic patches on the protein surface. These two arrangements suggest that the methionine motifs might function in proteinprotein interactions between PcoC molecules or with other methionine-rich proteins such as PcoA. Analytical ultracentrifugation data indicate that a weak monomerdimer equilibrium exists in solution for the apo protein. Dimerization is significantly enhanced upon binding Cu(I) with a measured Δ(ΔG°)≤-8.0 kJ/mole, suggesting that copper might bind at the dimer interface.
Original language | English (US) |
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Pages (from-to) | 185-194 |
Number of pages | 10 |
Journal | Journal of Biological Inorganic Chemistry |
Volume | 8 |
Issue number | 1-2 |
DOIs | |
State | Published - Jan 2003 |
Funding
Acknowledgements This work was supported by NSF grants MCB-9874408 (A. C. R.) and DBI-9974819 (B. D.) and NIH grants GM54111 (T. V. O), GM08061 (A. K. W.), and ES07284 (D. L. H.). L.A.F acknowledges support as a Fellow of the Fannie and John Hertz Foundation. We thank A. L. Lamb for assistance with crystallographic refinement, L. Pascoli for assistance with crystal growth, and K. Spiegel of the Keck Biophysics Facility at North-western University for assistance with the analytical ultracentrifugation experiments and use of the facility (http:// www.biochem.northwestern.edu/Keck/keckmain.html).
Keywords
- Copper resistance
- Metallochaperone
- Methionine motif
- PcoA
- PcoC
ASJC Scopus subject areas
- Biochemistry
- Inorganic Chemistry
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Dive into the research topics of 'Crystal structure and dimerization equilibria of PcoC, a methionine-rich copper resistance protein from Escherichia coli'. Together they form a unique fingerprint.Datasets
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Crystal Structure of PcoC, a Methionine Rich Copper Resistance Protein from Escherichia coli
Wernimont, A. K. (Contributor), Huffman, D. L. (Contributor), Finney, L. A. (Contributor), Demeler, B. (Contributor), O'Halloran, T. V. (Contributor) & Rosenzweig, A. C. (Contributor), Protein Data Bank (PDB), Nov 27 2002
DOI: 10.2210/pdb1LYQ/pdb, https://www.wwpdb.org/pdb?id=pdb_00001lyq
Dataset
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Crystal Structure of Selenomethionine PcoC, a Copper Resistance Protein from Escherichia coli
Wernimont, A. K. (Contributor), Huffman, D. L. (Contributor), Finney, L. A. (Contributor), Demeler, B. (Contributor), O'Halloran, T. V. (Contributor) & Rosenzweig, A. C. (Contributor), Protein Data Bank (PDB), Nov 27 2002
DOI: 10.2210/pdb1IX2/pdb, https://www.wwpdb.org/pdb?id=pdb_00001ix2
Dataset