title: AtHMA1 contributes to the detoxification of excess Zn(II) in Arabidopsis.
abstract: AtHMA1 is a member of the heavy metal-transporting ATPase family. It exhibits amino acid sequence similarity to two other Zn(II) transporters, AtHMA2 and AtHMA4, and contains poly-His motifs that are commonly found in Zn(II)-binding proteins, but lacks some amino acids that are typical for this class of transporters. AtHMA1 localizes to the chloroplast envelope. In comparison with wild-type plants, we observed a more pronounced sensitivity in the presence of high Zn(II) concentrations, and increased accumulation of Zn in the chloroplast of T-DNA insertional mutants in AtHMA1. The Zn(II)-sensitive phenotype of AtHMA1 knock-out plants was complemented by the expression of AtHMA1 under the control of its own promoter. The Zn(II)-transporting activity of AtHMA1 was confirmed in a heterologous expression system, Saccharomyces cerevisiae. The sensitivity of yeast to high concentrations of Zn(II) was altered by the expression of AtHMA1 lacking its N-terminal chloroplast-targeting signal. Taken together, these results suggest that under conditions of excess Zn(II), AtHMA1 contributes to Zn(II) detoxification by reducing the Zn content of Arabidopsis thaliana plastids.
authors.affiliation: POSTECH-UZH Global Research Laboratory, Division of Molecular Life Sciences, Pohang University of Science and Technology, Pohang, Korea.
authors.forename: Yu-Young
authors.initials: YY
authors.lastname: Kim
authors.forename: Hyunju
authors.initials: H
authors.lastname: Choi
authors.forename: Shoji
authors.initials: S
authors.lastname: Segami
authors.forename: Hyung-Taeg
authors.initials: HT
authors.lastname: Cho
authors.forename: Enrico
authors.initials: E
authors.lastname: Martinoia
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Maeshima
authors.forename: Youngsook
authors.initials: Y
authors.lastname: Lee
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism*; D003001:Cloning, Molecular; D018506:Gene Expression Regulation, Plant; D055786:Gene Knockout Techniques; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D018520:Plant Shoots / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D016415:Sequence Alignment; D015032:Zinc / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D018749:RNA, Plant; D000251:Adenosine Triphosphatases; C509978:HMA1 protein, Arabidopsis; D015032:Zinc