Magnetite Nanoparticles Biomineralization in the Presence of the Magnetosome Membrane Protein MamC: Effect of Protein Aggregation and Protein Structure on Magnetite Formation

Abstract

MamC from Magnetococcus marinus MC-1 has been shown to control the size of magnetite crystals in in vitro experiments, thereby demonstrating its potential as a candidate protein for the production of magnetite nanoparticles possibly useful in medical and other applications. However, the importance of the structure and aggregation state of the protein on the resulting biomimetic nanoparticles has not yet been assessed. One method normally used to prevent the aggregation of integral membrane proteins is the introduction of detergents during protein purification. In this study, results from protein aggregation following the addition of Triton-X100, DDM, and LDAO are presented. Magnetite particles formed in the presence of MamC purified using these three detergents were compared. Our results show that detergents alter the structure of the folded recombinant protein, thus preventing the ability of MamC to control the size of magnetite crystals formed chemically in vitro. Furthermore, we show that the introduction of detergents only at the dialysis process during the protein purification prevents its aggregation and allows for correct, functional folding of MamC. These results also indicate that the population of the active protein particles present at a certain oligomeric state needs to be considered, rather than only the oligomeric state, in order to interpret the ability of magnetosome recombinant proteins to control the size and/or morphology of magnetite crystals formed chemically in vitro.

The importance of the helical structure of a MamC-derived magnetite-interacting peptide for its function in magnetite formation

“…This hypothesis is supported by our previous results, in which a short fragment from MamC-MIC (Arg61-Gly77) did not interact with magnetite particles, most likely owing to the lack of a defined MIC structure (Nudelman et al, 2016). This result is in agreement with the conclusion that MamC must be well structured in order to play a role in magnetite growth, as reflected by effects on the size of the crystals (Lopez-Moreno et al, 2017).…”

“…1c), while in the helical MIC structure this distance is only 8 Å (Fig. 1d), a value that fits the distance between two Fe atoms on the (111), (100), (311) and (110) magnetite faces (Nudelman et al, 2016;Lopez-Moreno et al, 2017). Although the distance between these amino acids in the MC R354 structure can change owing to the high flexibility of the MIC structure, the probability of the moiety forming a stable structure that is able to interact with the magnetite surface is low.…”

Effects of Environmental Conditions on High-Yield Magnetosome Production by Magnetospirillum gryphiswaldense MSR-1

“…mM), as compared to the higher concentrations (60 mM), which support previous results [38] . Proteins promote the nucleation of iron crystals, leading to magnetosome production in magnetotactic bacteria after the vesicles assembling [39] . It has recently been illustrated that the magnetosome-associated membrane proteins play a significant role in magnetosome crystals growth inside the magnetotactic bacteria [39,40] .…”

“…Proteins promote the nucleation of iron crystals, leading to magnetosome production in magnetotactic bacteria after the vesicles assembling [39] . It has recently been illustrated that the magnetosome-associated membrane proteins play a significant role in magnetosome crystals growth inside the magnetotactic bacteria [39,40] . Our result showed that within 50-h culture, a maximum amount of magnetosome was produced (about 186.87 mg L −1 ), and 5.76 g L −1 bacterial cells were obtained, whereas the cell growth rate was 2.768 g L −1 /day.…”

Functionalized Biomimetic Magnetic Nanoparticles as Effective Nanocarriers for Targeted Chemotherapy

“…, and high‐resolution transmission electron microscopy (HRTEM) analyses in ref. and are not included here. According to these results, the BMNPs used in the present study are super‐paramagnetic magnetic nanoparticles at 300 K, composed of ≈95 wt% of magnetite and ≈5 wt% of MamC, with an isoelectric point of 4.4 and specific surface area of 90 m 2 g −1 .…”