title: Large Mg(2+)-dependent currents are associated with the increased expression of ALR1 in Saccharomyces cerevisiae.
abstract: Two genes in Saccharomyces cerevisiae, ALR1 and ALR2, encode proteins putatively involved in Mg(2+) uptake. The present study supports this role for ALR1 and provides the first electrophysiological characterisation of this protein. The patch-clamp technique was used to measure whole-cell ion currents in protoplasts prepared from the wild-type strain, the alr1 alr2 double mutant (CM66), and the double mutant over-expressing the ALR1 gene (CM66+ALR1). With 50 mM Mg(2+) in the bathing solution, the inward current in protoplasts of CM66+ALR1 averaged -264+/-48 pA at -150 mV. Inward currents measured in the wild-type and CM66 protoplasts were more than five-fold smaller. When Mg(2+) was the major cation in the pipette solution, time-dependent outward currents were also detected in CM66+ALR1 protoplasts suggesting ALR1 can facilitate Mg(2+) efflux as well as uptake. We conclude that the ALR1 gene encodes a transport protein. The large magnitude of the Mg(2+)-dependent currents suggests that ALR1 could function as a cation channel.
authors.affiliation: Department of Health Sciences, University of Technology, Sydney, P.O. Box 123, Broadway, NSW, 2007, Australia.
authors.forename: Guo Jun
authors.initials: GJ
authors.lastname: Liu
authors.forename: Donald K
authors.initials: DK
authors.lastname: Martin
authors.forename: Richard C
authors.initials: RC
authors.lastname: Gardner
authors.forename: Peter R
authors.initials: PR
authors.lastname: Ryan
mesh_terms: D001692:Biological Transport; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D027682:Cation Transport Proteins; D004594:Electrophysiology; D015870:Gene Expression; D007473:Ion Channels / Q000502:physiology; D008274:Magnesium / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism* / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins / Q000096:biosynthesis / Q000235:genetics*
chemical_list: C110206:ALR1 protein, S cerevisiae; D002352:Carrier Proteins; D027682:Cation Transport Proteins; D007473:Ion Channels; D029701:Saccharomyces cerevisiae Proteins; D008274:Magnesium