title: A combined zinc/cadmium sensor and zinc/cadmium export regulator in a heavy metal pump.
abstract: Heavy metal pumps (P1B-ATPases) are important for cellular heavy metal homeostasis. AtHMA4, an Arabidopsis thaliana heavy metal pump of importance for plant Zn(2+) nutrition, has an extended C-terminal domain containing 13 cysteine pairs and a terminal stretch of 11 histidines. Using a novel size-exclusion chromatography, inductively coupled plasma mass spectrometry approach we report that the C-terminal domain of AtHMA4 is a high affinity Zn(2+) and Cd(2+) chelator with capacity to bind 10 Zn(2+) ions per C terminus. When AtHMA4 is expressed in a Zn(2+)-sensitive zrc1 cot1 yeast strain, sequential removal of the histidine stretch and the cysteine pairs confers a gradual increase in Zn(2+) and Cd(2+) tolerance and lowered Zn(2+) and Cd(2+) content of transformed yeast cells. We conclude that the C-terminal domain of AtHMA4 serves a dual role as Zn(2+) and Cd(2+) chelator (sensor) and as a regulator of the efficiency of Zn(2+) and Cd(2+) export. The identification of a post-translational handle on Zn(2+) and Cd(2+) transport efficiency opens new perspectives for regulation of Zn(2+) nutrition and tolerance in eukaryotes.
authors.affiliation: Department of Plant Biology and Biotechnology, Centre for Membrane Pumps in Cells and Disease, PUMPKIN, Danish National Research Foundation, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark.
authors.forename: Lone
authors.initials: L
authors.lastname: Baekgaard
authors.forename: Maria D
authors.initials: MD
authors.lastname: Mikkelsen
authors.forename: Danny M
authors.initials: DM
authors.lastname: Sørensen
authors.forename: Josefine N
authors.initials: JN
authors.lastname: Hegelund
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Persson
authors.forename: Rebecca F
authors.initials: RF
authors.lastname: Mills
authors.forename: Zhang
authors.initials: Z
authors.lastname: Yang
authors.forename: Søren
authors.initials: S
authors.lastname: Husted
authors.forename: Jens Peter
authors.initials: JP
authors.lastname: Andersen
authors.forename: Morten J
authors.initials: MJ
authors.lastname: Buch-Pedersen
authors.forename: Jan K
authors.initials: JK
authors.lastname: Schjoerring
authors.forename: Lorraine E
authors.initials: LE
authors.lastname: Williams
authors.forename: Michael G
authors.initials: MG
authors.lastname: Palmgren
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002104:Cadmium / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D017136:Ion Transport / Q000502:physiology; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D015032:Zinc / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D027682:Cation Transport Proteins; D002104:Cadmium; D000251:Adenosine Triphosphatases; C477864:HMA4 protein, Arabidopsis; D015032:Zinc