Mg2+-ATP Sensing in CNNM, a Putative Magnesium Transporter.Chen, Y.S., Kozlov, G., Fakih, R., Yang, M., Zhang, Z., Kovrigin, E.L., Gehring, K.
(2020) Structure 28: 324-335.e4
- PubMed: 31864811
- DOI: 10.1016/j.str.2019.11.016
- Structures With Same Primary Citation
- PubMed Abstract:
The family of cystathionine-β-synthase (CBS)-pair domain divalent metal cation transport mediators (CNNMs) is composed of four integral membrane proteins associated with Mg 2+ transport. Structurally, CNNMs contain large cytosolic regions ...
The family of cystathionine-β-synthase (CBS)-pair domain divalent metal cation transport mediators (CNNMs) is composed of four integral membrane proteins associated with Mg 2+ transport. Structurally, CNNMs contain large cytosolic regions composed of a CBS-pair and a cyclic nucleotide-binding homology (CNBH) domain. How these regulate Mg 2+ transport activity is unknown. Here, we determined the crystal structures of cytosolic fragments in two conformations: Mg 2+ -ATP-analog bound and ligand free. The structures reveal open and closed conformations with functionally important contacts not observed in structures of the individual domains. We also identified a second Mg 2+ -binding region in the CBS-pair domain and a different dimerization interface for the CNBH domain. Analytical ultracentrifugation and isothermal titration calorimetry experiments revealed a tight correlation between Mg 2+ -ATP binding and protein dimerization. Mutations that blocked either function prevented cellular Mg 2+ efflux activity. The results suggest Mg 2+ efflux is regulated by conformational changes associated with Mg 2+ -ATP binding to CNNM CBS-pair domains.
Department of Biochemistry & Centre for Structural Biology, McGill University, Montreal, QC H3G 0B1, Canada. Electronic address: email@example.com.