P-type ATPase transporters utilize ATP hydrolysis to import or export ions or other substrates into the cell, sustaining key electrochemical gradients and ion homeostasis. This family of proteins uses a highly conserved post-Albers cycle mechanism which transitions the membrane protein through multiple states—E1, E1P, E2P, and E2—to transport ions/substrates across the membrane. Numerous monomer structures of P-type ATPases have been solved across species and in multiple intermediate states of the post-Albers cycle. Although monomers have catalytic activity, experimental evidence from multiple P-type ATPases support the idea that multimeric P-types exist in vivo. Evidence of a multimeric hypothesis was present in low resolution cryo-EM densities, kinetic studies, and FRET studies dating as far back as the late 1970s. Recent data has shown that SERCA, often seen as the model system for P-type ATPases, has significantly increased Ca 2+ transport and catalytic efficiency in the dimer state. Furthermore, our recent cryo-EM work has solved an E. coli MgtA dimer structure. MgtA, a magnesium transporter, is also evolutionarily related to other P-type ATPases—Na + , K + -ATPase, H + -ATPase Pma1, etc.—have been shown to be functional multimers across multiple species. Here, we investigate whether a functional dimeric MgtA exists in another pathogenic species with high sequence similarity to E. coli , using single-particle cryogenic electron microscopy and functional assays. This evidence would further support the claim that multimeric P-type ATPases correspond with the native functional unit. Properly understanding the native structure and mechanism behind the transporter may enable the development of novel therapeutics.
Satwik Vakada (Sun,) studied this question.