An Iron-Sulfur System
There are several molecules that have iron and sulfur
bonded together in various arrangements. One common arrangement
contains four sulfur atoms and four iron atoms together in a structure.
This was seen in the aldehyde ferredoxin oxidoreductase on the
Isolated Non-heme Iron page.
Nitrogenase is an enzyme that is very important in maintaining
the natural nitrogen cycle. It is found in bacteria and is used in
the breakdown of N2 into ammonia during nitrogen fixation.
The molecule has two interesting iron-sulfur groups.
This is one of the two groups. It contains two
Fe4S4 clusters
linked by a sulfur-sulfur bond. It is often referred to as a
"P-cluster pair."
This view shows what happens to the iron-sulfur cluster
when a few of the surrounding groups are added. From
this view an interesting bit of knowledge about the structure can be
seen. Two of the iron atoms on opposite corners are bonded to another
sulfur atom, which is part of a cysteine molecule.
The second iron-sulfur group is interesting because it is a symetrical
group with an iron on one end and a molybdenum at the other.
This view shows what the group looks like with the end iron and molybdenum having the
connecting molecules
in the picture. The tetrahedral geometry of the end iron is very clear, and the
interesting
distorted octahedral geometry found around the molybdenum is also shown.
Iron in a Heme Group
Isolated Non-Heme Iron
Two Other Interesting Proteins
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