[摘要]：Background: Databases include many putative prokaryotic Na+/Ca2+ exchangers, but none have been functionally expressed. Results: A membrane protein (MaX1) of Methanosarcina acetivorans catalyzes electrogenic countertransport of Na+ and Ca2(+). Conclusion: MaX1 has properties similar to those of mammalian Na+/Ca2+ exchangers. Significance: The characterization and purification of MaX1 should facilitate structure/function studies.
