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