A combined zinc/cadmium sensor and zinc/cadmium export regulator in a heavy metal pump.
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.
Baekgaard
Lone
L
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.
Mikkelsen
Maria D
MD
Sørensen
Danny M
DM
Hegelund
Josefine N
JN
Persson
Daniel P
DP
Mills
Rebecca F
RF
Yang
Zhang
Z
Husted
Søren
S
Andersen
Jens Peter
JP
Buch-Pedersen
Morten J
MJ
Schjoerring
Jan K
JK
Williams
Lorraine E
LE
Palmgren
Michael G
MG
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*
D029681:Arabidopsis Proteins; D027682:Cation Transport Proteins; D002104:Cadmium; D000251:Adenosine Triphosphatases; C477864:HMA4 protein, Arabidopsis; D015032:Zinc