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PMID:9430719

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Citation

MacDiarmid, CW and Gardner, RC (1998) Overexpression of the Saccharomyces cerevisiae magnesium transport system confers resistance to aluminum ion. J. Biol. Chem. 273:1727-32

Abstract

Ionic aluminum (Al3+) is toxic to plants, microbes, fish, and animals, but the mechanism of its toxicity is unknown. We describe the isolation of two yeast genes (ALR1 and ALR2) which confer increased tolerance to Al3+ and Ga3+ ions when overexpressed while increasing strain sensitivity to Zn2+, Mn2+, Ni2+, Cu2+, Ca2+, and La3+ ions. The Alr proteins are homologous to the Salmonella typhimurium CorA protein, a bacterial Mg2+ and Co2+ transport system located in the periplasmic membrane. Yeast strains lacking ALR gene activity required additional Mg2+ for growth, and expression of either ALR1 or ALR2 corrected the Mg(2+)-requiring phenotype. The results suggest that the ALR genes encode the yeast uptake system for Mg2+ and other divalent cations. This hypothesis was supported by evidence that 57Co2+ accumulation was elevated in ALR-overexpressing strains and reduced in strains lacking ALR expression. ALR overexpression also overcame the inhibition of Co2+ uptake by Al3+ ions. The results indicate that aluminum toxicity to yeast occurs as a consequence of reduced Mg2+ influx via the Alr proteins. The molecular identification of the yeast Mg2+ transport system should lead to a better understanding of the regulation of Mg2+ homeostasis in eukaryote cells.

Links

PubMed

Keywords

Aluminum/toxicity; Amino Acid Sequence; Biological Transport, Active/genetics; Carrier Proteins/genetics; Carrier Proteins/metabolism; Cation Transport Proteins; Cloning, Molecular; Cobalt/metabolism; Drug Resistance/genetics; Gene Library; Magnesium/metabolism; Molecular Sequence Data; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins

Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

YEAST:ALR2

enables

GO:0022890: inorganic cation transmembrane transporter activity

ECO:0000315: mutant phenotype evidence used in manual assertion

F

Seeded From UniProt

complete

YEAST:ALR2

involved_in

GO:0006812: cation transport

ECO:0000315: mutant phenotype evidence used in manual assertion

P

Seeded From UniProt

complete

YEAST:ALR2

located_in

GO:0005886: plasma membrane

ECO:0000315: mutant phenotype evidence used in manual assertion

C

Seeded From UniProt

complete

YEAST:ALR2

involved_in

GO:0055085: transmembrane transport

ECO:0000315: mutant phenotype evidence used in manual assertion

P

Seeded From UniProt

complete

YEAST:ALR1

enables

GO:0022890: inorganic cation transmembrane transporter activity

ECO:0000315: mutant phenotype evidence used in manual assertion

F

Seeded From UniProt

complete

YEAST:ALR1

involved_in

GO:0006812: cation transport

ECO:0000315: mutant phenotype evidence used in manual assertion

P

Seeded From UniProt

complete

YEAST:ALR1

located_in

GO:0005886: plasma membrane

ECO:0000315: mutant phenotype evidence used in manual assertion

C

Seeded From UniProt

complete

See also

References

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