Depicting the function of the magnetosome-associated protein Mms7 is important for further understanding the formation of magnetite by magnetotactic bacteria, and from a biotechnological point of view, for the synthesis of magnetosome-like biomimetic magnetic nanoparticles (BMNPs). In this work, the role of Mms7 (Magnetococcus marinus MC-1) in magnetite precipitation was analyzed by using this protein to in vitro produce BMNPs (Mms7-BMNPs). The new nanoparticles were characterized (X-ray diffraction, electron microscopy, magnetic properties, surface area, thermogravimetry, infrared spectroscopy, electrophoretic mobility and hyperthermia) and compared with MamC-mediated BMNPs (MamC-BMNPs) and inorganic (protein-free) magnetic nanoparticles (MNPs). Results suggest that the N-terminus of Mms7 induces the nucleation of magnetite and stabilizes the nuclei, which later dissolve to provide iron for the growth of larger crystals formed at the C-terminus. We hypothesize that the acidic amino acids in the C-terminus block the growth of (311) and (110) crystal faces, that show up in the final morphology along with the (111) faces already present in MNPs. The resulting Mms7-BMNPs are similar to MamC-BMNPs in terms of size (⁓33 nm) and morphology, but their magnetic saturation (43.7 emu/g) and their ability to raise the temperature when exposed to alternating magnetic fields is lower. However, the heating efficiency upon laser irradiation in the near infrared is similar in all cases. The changes in Mms7-BMNPs are probably related to a higher protein content (⁓8 wt%) attached to the magnetic core, which also provides an isoelectric point of ⁓4.7 to the nanoparticles and allows cell uptake and drug binding/release based on electrostatic interactions.