ISBN: 978-83-60043-10-3 - eurobic9

P. Turano
Eurobic9, 2-6 September, 2008, Wrocław, Poland
SL9. NMR of Ferritin: a 480 kDa Protein
CERM & Department of Chemistry, University of Florence, Via Luigi Sacconi, 6, 50019, Sesto Fiorentino
(Florence), Italy
e-mail: turano@cerm.unifi.it
We report here about the NMR characterization of the 480 kDa protein bullfrog ferritin M. The protein is a
homopolymer of 24 identical subunits forming a large hollow sphere. Each subunit has 175 amino acids folded
into four helix bundles; in living cells the cavity contains concentrated iron (hydrated ferric oxide mineral). The
protein is assembled as a spherical nanocage with an external diameter of 12 nm, and an inner cavity, 8 nm in
diameter.A combined solution-solid state approach was developed by us to assign the signals of such a large
system in its apo form. By exploiting 13 C-resonance-specific chemical shifts and spin diffusion effects, by 13 Cdirect
detection NMR in solution we identified 75% of the spin patterns of protein amino acids, with intraresidue
C-C connectivities between nuclei separated by 1-4 bonds [1, 2]. Solid state NMR provided sequence specific
assignments [3].Paramagnetic protonless NMR in solution was successfully used to identify the channel through
which iron(III) migrates from the ferroxidase site to the internal nanocompartment where the mineral is formed.
References:
[1] Matzapetakis, M., Turano, P., Theil, E. C., and Bertini, I., 13 C- 13 C NOESY spectra of a 480 kDa protein:
solution NMR of ferritin, J.Biomol. NMR, 38, 237-242, 2007.
[2] Bermel, W., Felli, I. C., Matzapetakis, M., Pierattelli, R., Theil, E. C., and Turano, P., A method for Cα
direct-detection in protonless NMR, J.Magn.Reson., 188, 301-310, 2007.
[3] Bertini, I., Felli, I. C., Klein, R., Lalli, D., Matzapetakis, M., Theil, E. C., and Turano, P. Solid state NMR of
ferritin, in preparation.
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