Assembly dynamics of magnetotactic bacterial actin-like protein MamK under shielded geomagnetic fields: In vitro evidence of inhibited filament formation.

The geomagnetic field (GMF) influences biological processes across diverse species, however, the molecular mechanisms underlying magnetoreception remain poorly understood. In this study, we examined the effects of hypomagnetic field (HypoMF) conditions-where the GMF is effectively shielded-on the assembly dynamics of the bacterial actin-like protein MamK in Magnetospirillum magneticum AMB-1. Through in vitro assays, we observed that HypoMF conditions disrupt MamK assembly, diminishing its ability to form elongated filaments. Notably, HypoMF enhances the release of inorganic phosphate during ATP hydrolysis, thereby destabilizing MamK filaments and promoting their disassembly. These findings suggest that the GMF contributes to the stabilization of MamK filaments, while HypoMF accelerates their disassembly, resulting in shorter filaments and increased non-specific aggregation. Our in vitro results underscore the critical role of geomagnetic conditions in regulating MamK assembly and filament formation, offering insights into the molecular basis of magnetoreception. Furthermore, historical geomagnetic reversals may have influenced the navigational capabilities and intracellular organization of magnetotactic bacteria by altering magnetosome chain structure.