Magnesium Transporters: Properties, Regulation and Structure

摘要: The chemistry of Mg2+ is unique amongst biological cations, and the properties transport systems reflect this chemistry. Prokaryotes carry three classes systems: CorA, MgtA/B MgtE. CorA MgtE are widely distributed in both Eubacteria Archaea, while class found primarily Eubacteria. Eukaryotic homologs although clearly functional as transporters, have minimal sequence homology include Mrs2p mitochondrial channel ALR proteins fungi. more recognizable eukaryotes SLC41 transporters. transporters belong to P-type ATPase superfamily, but mediate influx down its electrochemical gradient rather than against with other ATPases. Their physiological role not clear. only transporter whose structure has been solved. It a homopentamer two transmembrane domains per monomer, first which forms ion conduction pathway. involves binding fully hydrated cation an extracellular loop connecting domains. Passage through membrane no electrostatic interactions, cytosolic domains, one carrying extremely high concentrations positive charge negative appear help control flux, concert intracellular bound between each monomer. Neither nor be transcriptionally regulated, implying they "housekeeping" genes. Nonetheless, mutation corA gene Salmonella enterica serovar Typhimurium leads attenuation virulence defects, even though strain carries additional mutant exhibits Mg2+-dependent growth deficit.