Crystal structure of an archaeal CorB magnesium transporter

CNNM/CorB proteins are a broadly conserved family of integral membrane proteins with close to 90,000 protein sequences known. They are associated with Mg2+ transport but it is not known if they mediate transport themselves or regulate other transporters. Here, we determine the crystal structure of an archaeal CorB protein in two conformations (apo and Mg2+-ATP bound). The transmembrane DUF21 domain exists in an inward-facing conformation with a Mg2+ ion coordinated by a conserved -helix. In the absence of Mg2+-ATP, the CBS-pair domain adopts an elongated dimeric configuration with previously unobserved domain-domain contacts. Hydrogen-deuterium exchange mass spectrometry, analytical ultracentrifugation, and molecular dynamics experiments support a role of the structural rearrangements in mediating Mg2+-ATP sensing. Lastly, we use an in vitro, liposome-based assay to demonstrate direct Mg2+ transport by CorB proteins. These structural and functional insights provide a framework for understanding function of CNNMs in Mg2+ transport and associated diseases. CNNM/CorB proteins are a conserved family of membrane proteins associated with Mg2+ transport. Here, structures of an archaeal CorB protein in apo state and with Mg2+-ATP bound and accompanying biophysical experiments suggest direct Mg2+ transport by CorB proteins.

Automated summary

CNNM/CorB proteins are a family of membrane proteins associated with Mg2+ transport. Structural studies on an archaeal CorB protein in apo state and with Mg2+-ATP bound, along with biophysical experiments, suggest the direct transport of Mg2+ by CorB proteins.