Abstract
This paper describes the design and characterization of a novel ferritin chimera. The iron storage protein ferritin forms a paramagnetic ferrihydrite core. This biomineral, when placed in a magnetic field, can decrease the transverse NMR relaxation times (T 2 and T 2*) of nearby mobile water protons. Ferritin nucleic acid constructs have recently been studied as “probeless” magnetic resonance imaging (MRI) reporters. Following reporter expression, ferritin sequesters endogenous iron and imparts hypointensity to T 2- and T 2*-weighted images in an amount proportional to the ferritin iron load. Wild-type ferritin consists of various ratios of heavy H and light L subunits, and their ratio affects ferritin’s stability and iron storage capacity. We report a novel chimeric ferritin with a fixed subunit stoichiometry obtained by fusion of the L and the H subunits (L*H and H*L) using a flexible linker. We characterize these supramolecular ferritins expressed in human cells, including their iron loading characteristics, hydrodynamic size, subcellular localization, and effect on solvent water T 2 relaxation rate. Interestingly, we found that the L*H chimera exhibits a significantly enhanced iron loading ability and T 2 relaxation compared to wild-type ferritin. We suggest that the L*H chimera may be useful as a sensitive MRI reporter molecule.
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Abbreviations
- AdV5:
-
Adenovirus type 5
- L*H, H*L:
-
Chimeric fusion ferritins
- DLS:
-
Dynamic light scatter
- H:
-
Heavy-chain ferritin
- IRP2:
-
Iron-responsive protein 2
- L:
-
Light-chain ferritin
- MRI:
-
Magnetic resonance imaging
- PAGE:
-
Polyacrylamide gel electrophoresis
- R 2 :
-
Transverse relaxation rate
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Acknowledgments
We acknowledge valuable technical assistance from Hongyan Xu and Joseph Suhan. We thank Kevin Hitchens for editorial assistance. We acknowledge support from the National Institutes of Health via grants R01-EB005740, P01-HD047675 and P41-EB001977 and a National Science Foundation Graduate Research Fellowship to B.I. (2007053507).
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Iordanova, B., Robison, C.S. & Ahrens, E.T. Design and characterization of a chimeric ferritin with enhanced iron loading and transverse NMR relaxation rate. J Biol Inorg Chem 15, 957–965 (2010). https://doi.org/10.1007/s00775-010-0657-7
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DOI: https://doi.org/10.1007/s00775-010-0657-7