title: Cation hexaammines are selective and potent inhibitors of the CorA magnesium transport system.
abstract: Cation hexaammines and related compounds are chemically stable analogs of the hydrated form of cations, particularly Mg(2+). We tested the ability of several of these compounds to inhibit transport by the CorA or MgtB Mg(2+) transport systems or the PhoQ receptor kinase for Mg(2+) in Salmonella typhimurium. Cobalt(III)-, ruthenium(II)-, and ruthenium(III)-hexaammines were potent inhibitors of CorA-mediated influx. Cobalt(III)- and ruthenium(III)chloropentaammines were slightly less potent inhibitors of CorA. The compounds inhibited uptake by the bacterial S. typhimurium CorA and by the archaeal Methanococcus jannaschii CorA, which bear only 12% identity in the extracellular periplasmic domain. Cation hexaammines also inhibited growth of S. typhimurium strains dependent on CorA for Mg(2+) uptake but not of isogenic strains carrying a second Mg(2+) uptake system. In contrast, hexacyano-cobaltate(III) and ruthenate(II)- and nickel(II)hexaammine had little effect on uptake. The inhibition by the cation hexaammines was selective for CorA because none of the compounds had any effect on transport by the MgtB P-type ATPase Mg(2+) transporter or the PhoQ Mg(2+) receptor kinase. These results demonstrate that cation hexaammines are potent and highly selective inhibitors of the CorA Mg(2+) transport system and further indicate that the initial interaction of the CorA transporter is with a fully hydrated Mg(2+) cation.
authors.affiliation: Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4965, USA. lmk10@po.cwru.edu
authors.forename: L M
authors.initials: LM
authors.lastname: Kucharski
authors.forename: W J
authors.initials: WJ
authors.lastname: Lubbe
authors.forename: M E
authors.initials: ME
authors.lastname: Maguire
mesh_terms: D000588:Amines / Q000737:chemistry / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D002352:Carrier Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D027682:Cation Transport Proteins; D002412:Cations; D017136:Ion Transport; D008274:Magnesium / Q000378:metabolism*; D012486:Salmonella typhimurium / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism
chemical_list: D000588:Amines; D001426:Bacterial Proteins; D002352:Carrier Proteins; D027682:Cation Transport Proteins; D002412:Cations; C072716:CorA protein, Salmonella; D008274:Magnesium