3D Structure of cytochrome c oxidase

CPK Color Scheme

Cytochrome c oxidase is a membrane protein that uses several metal ions to transfer electrons to oxygen molecules in order to produce water and is the final step in the electron transport chain. In addition, this enzyme allows for protons to be pumped to the intermembrance space from the matrix, and this proton gradient contributes to ATP synthesis.

This resets the protein structure . Click here.

Click here to see the hydrophilic (blue) and hydrophobic (red) regions of the protein. The polar regions are concentrated towards the ends of the molecule while the nonpolar regions are concentrated in the center of the molecule. The polar regions probably interact with the cytoplasm while the nonpolar regions interact with the hydrophobic interior of the membrane.

Click here to see each of the 13 subunits contained in this enzyme.(This molecule is shown as a dimer and thus has 26 chains.)

Click here to see the heme structures embedded in this protein. Each monomer has two heme subunits, named heme a and heme a3.

This shows the Fe atoms(in blue) embedded within the heme groups. The presence of metal atoms within this enzyme allows electrons to be received, held, and ultimately transferred to oxygen. The metal receives the electron and is reduced, and it oxidizes again when the electron is transferred to another region of the molecule.

Click here to see the copper atoms (in orange).The 2 copper atoms close together, CuA, constitute the port of entry for the oxygen into the molecule and the oxygen is then trapped between the iron and the other copper atom, CuB.

The path of the electron is as follows: The electron is transferred to cytochrome c oxidase from cytochrome c. It is then transferred to CuA, then to heme a (farthest from CuB), and then to CuB and heme a3 where the electron is then used to reduce oxygen to water.

There is one other metal ion complexed with this molecule, Mg, which is shown in purple. Magnesium is involved in a channel that allows water to exit into the intermembrane space and allows protons to establish a gradient (needed for ATP synthesis).


< http://www.rcsb.org/pdb/molecules/pdb5_1.html>. Accessed 31 March 2003.

<http://www.chem.uwec.edu/Chem406_F97/Webpages97/jscott/cco2.html >. Accessed 31 March 2003.

Brzezinski, P. 1996. Internal Electron-Transfer Reactions in Cytochrome c Oxidase. Biochemistry. 35(18):5611-5615.

Hill, BC. 1994. Modeling the Sequence of Electron Transfer Reactions in the Single Turnover of Reduced, Mammalian Cytochrome c Oxidase with Oxygen." The Journal of Biological Chemistry.269(4):2419-2425.

Purves WK, Sadava D, Orians GH, Heller HC. 2001. Life: the Science of Biology, sixth edition. Sunderland, Massachusetts: Sinauer Associates, Inc.; p 283-284, 724, 905.


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