Researchers learned that, to get into cells, plutonium uses iron as a “trojan horse.” Image: Argonne National Laboratory |
Plutonium
gets taken up by our cells much as iron does, even though there’s far less of
it to go around.
Researchers
at the U.S. Department of Energy’s (DOE) Argonne National Laboratory and Northwestern University have identified a new
biological pathway by which plutonium finds its way into mammalian cells. The
researchers learned that, to get into cells, plutonium acts like a “Trojan
horse,” duping a special membrane protein that is typically responsible
for taking up iron.
This
discovery may help enhance the safety of workers who deal with plutonium, as
well as show the way to new bio-inspired approaches for separating radioactive
elements from other metals in used nuclear fuel.
Because
the bodies of mammals have evolved no natural ability to recognize plutonium, scientists
were curious to know the cellular mechanisms responsible for its retention in
the body. The researchers exposed adrenal cells from rats to minute quantities
of plutonium to see how the cells accumulated the radioactive material.
Using the
high-energy X-rays provided by Argonne’s
Advanced Photon Source, the researchers were able to characterize a particular
protein known as “transferrin,” which is responsible for bringing
iron into cells. Each transferrin is made up of two subunits, known as N and C,
that normally bind iron. When another protein—the transferrin
receptor—recognizes both the N and C subunits, it admits the molecule to the
cell. However, when both the N and C subunits contain plutonium, the
transferrin receptor doesn’t recognize the protein and keeps it out.
Contrary
to their expectations, the researchers discovered that in one of the mixed
states—when an iron-containing N-subunit is combined with a
plutonium-containing C-subunit—the resulting hybrid so closely resembles the
normal iron protein that the uptake pathway is “tricked” into allowing
plutonium to enter the cell.
“Although
the interaction between plutonium and bodily tissues has been studied for a
long time, this is the first conclusive identification of a specific pathway
that allows for the introduction of plutonium into cells,” said Mark
Jensen, an Argonne chemist who led the
research.
The
results of the study were published online on the Website of Nature Chemical Biology.
