Elucidation and Control of Actinide Trafficking Pathways in Mammalian Cells

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Elucidation and Control of Actinide Trafficking
Pathways in Mammalian Cells
Chuan He University of Chicago Department of
Chemistry
Mark P. Jensen Argonne National Lab Chemical
Sciences and Engineering Division
Sixth Argonne UChicago Fermilab Collaboration
Meeting, October 12, 2009
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The Nuclear Conundrum

• Nuclear Energy is a carbon-free source for 20 of
  U.S. world electricity production.
• Why not 80?
• Socio-economic reasons
• Cost and economic risk
• Proliferation of nuclear technology
• Public worries about safety
• Technical reason
• How do we handle the waste?

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Actinides? Really?
Recognizing metal ions with high selectivity and
sensitivity is essential for life. Nature has
evolved various metalloproteins to exploit and
control metals.
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Objectives
Create new ways to efficiently, economically, and
safely handle actinides when they are no longer
useful

• Discover how cells handle toxic human-made
  metals, the transuranium actinides
• Visualize actinide trafficking in cells with
  X-ray microbeams
• Identify individual proteins that bind actinides
  in mammalian cells
• Biochemically and structurally characterize
  actinide binding by various proteins

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Where do Actinides Accumulate in Cells?
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First Structures of Pu-Containing Proteins
One form of transferrin containing both plutonium
and iron has the same shape as the native
protein, which contains only iron.
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Blocking Pu Uptake by Cells Appears Possible
Images of rat adrenal gland cells Axes -
coordinates in mm
Bad Plutonium PuCFeNTf
Bad Plutonium plus 50 uM chloroquine
No Plutonium
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Could metal-binding proteins be redesigned to
bind actinides?
NikR
NikR is a transcriptional repressor for
expression of the nikABCDE operon in the presence
of excessive concentrations of intracellular
Ni2 Ref C. L. Drennan et al, Nat. Struc.
Biol., 2003, 10, 794-799 C. L. Drennan et al,
PNAS, 2006, 103, 13676-13681
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Design of an Actinyl Binding Site
MQRVTITLDD DLLETLDSLS QRRGYNNRSE AIRDILRSAL
AQEATQQHGT QGFAVLSYVY EHEKRDLASR IVSTQHHHHD
LSVATLHVHI NHDDCLEIAV LKGDMGDVQH FADDVIAQRG
VRHGHLQCLP KED Mutations V72 ? S V72SC95? D, H,
S V72S C95D H76? D,E V72S C95S H76? D,E
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Design of an Actinyl Binding Site
The Kd of uranyl binding to NikR was determined
to be 53 nM
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Uranyl Binding and Function
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Joint Publication
S. V. Wegner, H. Boyaci, H. Chen, M. P. Jensen,
C. He, Angew. Chem. Int. Ed. (2009), 48, 2339.
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Engineer bacteria to uptake, transport and store
actinides
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Design Peptides that are Selective for Specific
Actinides
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LBT DTNNDGWYEGDELLA