Metal-substituted protein MRI contrast agents engineered for enhanced relaxivity and ligand sensitivity
Author(s)Lelyveld, Victor S.; Brustad, Eric; Arnold, Frances H.; Jasanoff, Alan Pradip
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Engineered metalloproteins constitute a flexible new class of analyte-sensitive molecular imaging agents detectable by magnetic resonance imaging (MRI), but their contrast effects are generally weaker than synthetic agents. To augment the proton relaxivity of agents derived from the heme domain of cytochrome P450 BM3 (BM3h), we formed manganese(III)-containing proteins that have higher electron spin than their native ferric iron counterparts. Metal substitution was achieved by coexpressing BM3h variants with the bacterial heme transporter ChuA in Escherichia coli and supplementing the growth medium with Mn3+-protoporphyrin IX. Manganic BM3h variants exhibited up to 2.6-fold higher T1 relaxivities relative to native BM3h at 4.7 T. Application of ChuA-mediated porphyrin substitution to a collection of thermostable chimeric P450 domains resulted in a stable, high-relaxivity BM3h derivative displaying a 63% relaxivity change upon binding of arachidonic acid, a natural ligand for the P450 enzyme and an important component of biological signaling pathways. This work demonstrates that protein-based MRI sensors with robust ligand sensitivity may be created with ease by including metal substitution among the toolkit of methods available to the protein engineer.
DepartmentMassachusetts Institute of Technology. Department of Biological Engineering; Massachusetts Institute of Technology. Department of Brain and Cognitive Sciences; Massachusetts Institute of Technology. Department of Nuclear Science and Engineering
Journal of the American Chemical Society
American Chemical Society
Lelyveld, Victor S. et al. “Metal-Substituted Protein MRI Contrast Agents Engineered for Enhanced Relaxivity and Ligand Sensitivity.” Journal of the American Chemical Society (2011) 133 (4), pp 649–651.
Author's final manuscript