Escherichia coli MCR-1 Protein, His Tag

The MCR-1 protein, encoded by the *mcr-1* gene in Escherichia coli and other Enterobacteriaceae, is a phosphoethanolamine transferase. Its primary function is to modify the lipid A component of lipopolysaccharide (LPS) in the bacterial outer membrane by adding phosphoethanolamine. This modification significantly reduces the net negative charge of the membrane, thereby conferring resistance to colistin (polymyxin E), a last-resort antibiotic for treating multidrug-resistant Gram-negative infections. First reported in China in 2015, MCR-1 is notable because its gene is often plasmid-borne, enabling horizontal transfer between bacterial species and facilitating the rapid global spread of colistin resistance, posing a major public health threat.