The function of Alr1p of Saccharomyces cerevisiae in cadmium detoxification: Insights from phylogenetic studies and particle-induced X-ray emission

Abstract

Two genes in Saccharomyces cerevisiae, ALR1 and ALR2, encode transmembrane proteins involved in Mg2+ uptake. The present study investigates the phylogenetic relationship of Alr1p/Alr2p with bacterial CorA proteins and some proteins related to Mg2+ influx/efflux transport in mitochondrial and bacterial zinc transporters; including hydrophobic cluster analysis (HCA). The phylogenetic results indicate that the Alrp sequences of S. cerevisiae share a common carboxy-terminus with proteins related to zinc efflux transport. We also analyse the intracellular metal content by particle-induced X-ray emission (PIXE) after cell exposure to cadmium. The PIXE analysis of cadmium-exposed ALR mutants and wild-type yeast cells suggests that Alrp has a central role in cell survival in a cadmium-rich environment.

Oligomerization of the Mg2+‐transport proteins Alr1p and Alr2p in yeast plasma membrane

“…Dominant negative effects were also exerted by the mutations L750V and S795R of the mutant alleles alr1–1 and alr1–31 , which are located in the first and second TM domain, respectively. The conservative mutation from L750V is likely to affect the flexibility and integrity of a predicted hydrophobic core [21], which is presumably critical for Mg 2+ binding. The introduction of a positive charged amino acid in mutation S795R in the second TM domain is likely to alter the conformation of the transmembrane domain.…”

The CorA family: Structure and function revisited

“…ALR increases tolerance to Al 3+ and Ga 3+ ions when overexpressed in S. cerevisiae while increasing strain sensitivity to Zn 2+ , Mn 2+ , Ni 2+ , Cu 2+ , Ca 2+ , and La 3+ ions [52]. ALR proteins are also suggested to have a central role in cell survival in a cadmium-rich environment [53]. Programs for predicting TM stretches consistently predict two TM helices near the C termini of all of these proteins.…”

HowSaccharomyces cerevisiaecopes with toxic metals and metalloids

“…Alr1p, which is responsible for Mg uptake into cells, may also contribute to Cd tolerance. Mutation of the ALR1 gene results in Cd sensitivity and increased intracellular Cd levels (Kern et al, 2005), but it is not known whether Alr1p mediates Cd export. Ssu1p is a member of the major facilitator superfamily and is involved in sulphite efflux (Park & Bakalinsky, 2000).…”