Revisiting the Potential Functionality of the MagR Protein

Abstract

Recent findings have sparked great interest in the putative magnetic receptor protein MagR. However, in vivo experiments have revealed no magnetic moment of MagR at room temperature. Nevertheless, the interaction of MagR and MagR fusion proteins with silica-coated magnetite beads have proven useful for protein purification. In this study, we recombinantly produced two different MagR proteins in Escherichia coli BL21(DE3) to (1) expand earlier protein purification studies, (2) test if MagR can magnetize whole E. coli cells once it is expressed to a high cytosolic, soluble titer, and (3) investigate the MagR-expressing E. coli cells’ magnetic properties at low temperatures. Our results show that MagR induces no measurable, permanent magnetic moment in cells at low temperatures, indicating no usability for cell magnetization. Furthermore, we show the limited usability for magnetic bead-based protein purification, thus closing the current knowledge gap between theoretical considerations and empirical data on the MagR protein.

Proteins as nanomagnets and magnetoreceptors

“…In no case was an attempt made to co-express cryptochrome suggesting, perhaps, that it is not a prerequisite for MagR magnetization. However, Pekarsky et al found that E. coli cells overexpressing fruit-fly MagR had no measurable permanent magnetization at low temperature and attributed their limited success at protein purification to ionic rather than magnetic interactions (Pekarsky et al, 2021).…”