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Updated: Jun 18, 2026
10:23
Synthesis of Cationized Magnetoferritin for Ultra-fast Magnetization of Cells
Published on: December 13, 2016
Effective charge saturation in ferritin cages.
Takumi Kuwata1, Yuusuke Murakami1, Daisuke Sato1
1Department of Biosciences, Soka University, 1-236 Tangi-machi, Hachioji, Tokyo, 192-8577, Japan.
Scientific Reports
|June 16, 2026
Summary
Ferritin proteins have a maximum negative charge limit. Mutating surface residues surprisingly revealed that Escherichia coli and Pseudo-nitzschia multiseries ferritins possess maximal negative charges, unlike animal ferritins.
Area of Science:
- Biochemistry
- Structural Biology
- Protein Chemistry
Background:
- Ferritins are highly conserved metalloproteins that store iron.
- They assemble into spherical 24-subunit cages, crucial for cellular iron homeostasis.
- The surface charge of ferritins can influence their interactions and functions.
Purpose of the Study:
- To investigate the net charge limit of ferritin proteins.
- To explore the role of surface glutamate and aspartate residues in determining ferritin net charge.
- To compare the net charge characteristics of bacterial, marine diatom, and animal ferritins.
Main Methods:
- Site-directed mutagenesis was used to create net-charge mutants of Escherichia coli ferritin (EcFtn) and Pseudo-nitzschia multiseries ferritin (PmFtn).
- Nondenaturing polyacrylamide gel electrophoresis (PAGE) and ζ-potential measurements were employed to assess the effective negative charges of the wild-type and mutant proteins.
- Amino acid sequence analysis was performed to compare charge characteristics across different species.
Main Results:
- Contrary to expectations, increasing the number of glutamate (Glu) and aspartate (Asp) residues did not increase the effective negative charge of the mutant ferritins.
- Conversely, decreasing the number of Glu and Asp residues led to a decrease in effective negative charge.
- Both EcFtn and PmFtn exhibited properties suggesting they possess the maximum possible negative charges for their structures.
- Sequence analysis indicated that bacterial and plant ferritins generally have near-maximum negative charges, while animal ferritins have significantly fewer.
Conclusions:
- Ferritin proteins appear to have a physical limit to their net negative charge.
- EcFtn and PmFtn are likely at or near this maximal negative charge capacity.
- Significant differences in surface charge exist between bacterial/plant and animal ferritins, potentially impacting their biological roles.
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