A new pathway for vacuolar cadmium sequestration in Saccharomyces cerevisiae: YCF1-catalyzed transport of bis(glutathionato)cadmium.
The yeast cadmium factor (YCF1) gene encodes an MgATP-energized glutathione S-conjugate transporter responsible for the vacuolar sequestration of organic compounds after their S-conjugation with glutathione. However, while YCF1 was originally isolated according to its ability to confer resistance to cadmium salts, neither its mode of interaction with Cd2+ nor the relationship between this process and organic glutathione-conjugate transport are known. Here we show through direct comparisons between vacuolar membrane vesicles purified from Saccharomyces cerevisiae strain DTY167, harboring a deletion of the YCF1 gene, and the isogenic wild-type strain DTY165 that YCF1 mediates the MgATP-energized vacuolar accumulation of Cd-glutathione complexes. The substrate requirements, kinetics and Cd2+/glutathione stoichiometry of cadmium uptake and the molecular weight of the transport-active complex demonstrate that YCF1 selectively catalyzes the transport of bis(glutathionato)cadmium (Cd x +GS2). On the basis of these results--the Cd2+ hypersensitivity of DTY167, versus DTY165, cells, the inducibility of YCF1-mediated transport, and the rapidity and spontaneity of Cd-GS2 formation--this new pathway is concluded to contribute substantially to Cd2+ detoxification.
Li
Z S
ZS
Plant Science Institute, Department of Biology, University of Pennsylvania, Philadelphia 19104, USA.
Lu
Y P
YP
Zhen
R G
RG
Szczypka
M
M
Thiele
D J
DJ
Rea
P A
PA
D018528:ATP-Binding Cassette Transporters; D000255:Adenosine Triphosphate / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D002104:Cadmium / Q000493:pharmacokinetics*; D002451:Cell Compartmentation; D004137:Dinitrochlorobenzene / Q000494:pharmacology; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D015870:Gene Expression / Q000187:drug effects; D005978:Glutathione / Q000031:analogs & derivatives* / Q000378:metabolism / Q000493:pharmacokinetics / Q000494:pharmacology; D008658:Inactivation, Metabolic; D009942:Organometallic Compounds / Q000493:pharmacokinetics*; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D014617:Vacuoles / Q000378:metabolism*
D018528:ATP-Binding Cassette Transporters; D004137:Dinitrochlorobenzene; D005656:Fungal Proteins; D009942:Organometallic Compounds; D029701:Saccharomyces cerevisiae Proteins; C089179:YCF1 protein, S cerevisiae; C103703:bis(glutathionato)cadmium; D002104:Cadmium; C030190:S-(2,4-dinitrophenyl)glutathione; D000255:Adenosine Triphosphate; D005978:Glutathione