Page 176 - The Miracle of Protein

174 THE MIRACLE OF PROTEIN

The picture above, shows a simplified version of the system
that allows the iron to enter the bacteria. As can be seen in the
model, the bacteria membrane has two layers and the top layer
has receptors called FepA. This receptor recognizes the mole-
cules that built a complex with the iron element and takes them
to the region between the inner and outer membrane. The nec-

essary energy to open up the receptor is provided from the inte-
rior layer of the membrane, and by means of TonB-ExbB-ExbD
proteins, this energy is transferred to the receptors. 82
These proteins are found in large amounts on the cell
membrane especially when the need for iron molecules is high.
Another intermediary protein named FepB, transfers the iron
complex which had passed through the receptor, to the inner
membrane. On the inner membrane is a security door made up
of FepG and FepD proteins. This door recognizes the iron com-

plex and admits it to the cell with the help of several other pro-
teins. 83

Iron is an atom that needs care-
ful handling inside the atom. For
this reason, special mechanisms
were created to ensure it is
carried carefully in every stage.
It is almost like iron is carefully
passed on from hand to hand.