MgtA and MgtB: prokaryotic P-type ATPases that mediate Mg2+ influx.

摘要: The gram-negative bacteriumSalmonella typhimurium possesses three distinct Mg2+ transport systems, encoded by thecorA, mgtA, andmgtB loci. CorA system is the constitutive influx system. It can also mediate efflux at very high extracellular concentrations. In contrast, MgtA and MgtB systems are normally expressed only low A strain ofS. was constructed mutagenesis which lacks requires 100mM for growth. Using this strain, both were cloned complementation of strains inability to grow without supplementation. After sequencing further genetic analysis, appears be an operon composed themgtC genes (5′ 3′). downstreammgtB gene encodes 102 kDa protein sequence analysis clearly a P-type ATPase. Interestingly, while has relatively poor homology other known prokaryotic ATPases, it highly homologous mammalian reticular Ca2+-ATPases. MgtC 22.5 hydrophobic membrane that any protein. Transposon insertions in abolish uptake We hypothesize subunit ATPase involved either proper insertion into or possibly binding delivery subunit. recently been completed, too more similar eukaryotic than ATPases. Expression regulated concentration Mg2+. Transcription ofmgtB increased about 1000 fold lowering from 1 mM µM. Likewise, whenmgtB multicopy plasmid, decrease greatly increases transport. Under growth conditions limiting Mg2+, becomes dominant inS. typhimurium. Even so, since (and MgtA) unclear why cell energy ATP entry down large electrochemical gradient. Further studies structure-function energetics these novel ATPases should yield insights function general as well information regulation cellular fluxes.