Cytochrome C Oxidase: The Amazing Everyday Protein

Cytochrom C Oxidase from PDB #1OCO was generated with PyMol  

Cytochrome C oxidase is also known as Complex IV in the electron transport chain.  It transfers electrons and protons from reduced cytochrome C and conserves the free energy  by creating a proton gradient which is then used to drive the synthesis of ATP.  This is a metalloprotein that is in a super family of heme-copper containing proteins.  This protein is the final step in mitochondrial respiratory which is the principle energy-generating system for cells!  There are five metals located in the active site of cytochrome C oxidase which does redox chemistry with cytochrome C to transport protons to the inner membrane and to O₂.  This protein can take O₂ and create two waters by adding four protons yet makes sure four more protons gets to the inner membrane so that ATP can be generated.  Without Cytochrome C oxidase the whole energy-transducing process is shut down which leads to no energy being produced. 

Cytochrome C Oxidase or Complex IV

 There are four heme groups within cytochrome c oxidase.  Around these heme groups there are copper ions which help drive the formation of water and the proton gradient.  These coppers take the electrons from cytochrome c to then transfer to O_2. This process isn't done anywhere else and can only be done within cytochrome c oxidase!

Active Site of Cytochrome C Oxidase, from PDB #2GSM generated by PyMol

Subunit I and II with active site, from PDB #2GSM generated by PyMol

Cytochrome c oxidase doesn't silently kill you or attack your body.  In fact, it does the complete opposite.  This protein is able to take plain old electrons and protons and create the major energy source for your body as well as a waste product that most people wouldn't even consider waste.  Cytochrome c oxidase isn't in a super family for no reason, it has enough metal in it to put hemoglobin to shame as well as transfer protons across a membrane without needing any energy input at all.  Without this protein doing it's job, you wouldn't be able to survive. Other proteins have to get into your body to before they can do anything yet cytochrome c oxidase is already there.  So, when making your choice for protein of the year remember, cytochrome c oxidase lets you, be you.  

Citations:
Taanman, JanWillem. "Human Cytochrome c Oxidase: Structure, Function, and Deficiency." Journal of Bioenergetics and Biomembranes 29.2 (1997): 151-63. Print.
http://link.springer.com/article/10.1023%2FA%3A1022638013825?LI=true

Muramoto, Kazumasa, and Kunio Hirata. "A histidine residue acting as a controlling site for dioxygen reduction and proton pumping by cytochrome c oxidase." Biophysics 104.19 (2007): 7881-86. Web. 13 Apr. 2013.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1876541/

Tsukihara, Tomitake, and Kunitoshi Shimokata. "The low-spin heme of cytochrome c oxidase as the driving element of the proton-pumping process." Chemistry 100.26 (2003): 15304-09. Web. 13 Apr. 2013.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC307562/
Image Citation:
Yoshida, Masasuke, Eiro Muneyuki, and Toru Misabori. "ATP synthase — a marvellous rotary engine of the cell." Nature Reviews Molecular Cell Biology 2.9 (2001): 669-77. Print.

Information on Cytochrome C Oxidase

Cytochrome C oxidase is also known as Complex IV in the electron transport chain.  It transfers electrons and protons from reduced cytochrome C and conserves the free energy released by creating a proton gradient which is then used to drive the synthesis of ATP.  This is a metalloprotein that is in a superfamily of heme-copper containing proteins.  This protein is the final step in mitochondrial respiratory which is the principle energy-generating system for cells!  There are 5 metals located in the active site of cytochrome C oxidase which does redox chemistry with cytochrome C to gain electrons to transport to the inner membrane.  This protein can take O₂ and create water by adding protons yet makes sure the electrons get to the inner membrane so that ATP can be generated.  Without Cytochrome C oxidase the whole energy-transducing process is shut down which means no energy would be produced. 

 http://link.springer.com/article/10.1023%2FA%3A1022638013825?LI=true

As I mentioned before there is a redox reaction happening.  This redox reaction is actually regulated by a conformational shift within a histidine and an aspartic acid which is located right next to the active site which helps in opening and closing the active site from regulation.  This conformational change is like a T and R state of hemoglobin but just as important. The histidine is important in redox control of proton collecting as it is part of the D pathway. 

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1876541/

 There are also 2 heme groups within Cytochrome C oxidase.  These hemes help drive the active proton transport from the interior across the enzyme via a water channel to the waiting O­₂ molecule to form water.  This is via the D pathway which just refers to the proton and O₂ coming together to form water.  There are so many things going on in this protein it is incredible.  The heme gets oxidized and arg-38 opens up to the water channel.  When the heme is reduced the asp-51 is opened to the intermembrane space which then releases the proton into the space and returns to its position away from the intermembrane.  This is how we get energy!  Without this process our main way to get energy into a usable form is impossible.    

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC307562/

  

Also, who doesn’t love a protein that can be studied via NMR?

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3145682/

More Cytochrome C Oxidase Pictures

Cytochrome C Oxidase Pictures

Cytochrome C Oxidase Active Site