权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Molecular properties of metal-uptake systems supported by proton pumps in plant cells

植物细胞中质子泵支持的金属吸收系统的分子特性

基本信息

批准号：
18380064
负责人：
MAESHIMA Masayoshi
金额：
$ 10.85万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

项目摘要

We obtained the following results concerning Ca^<2+>/H^+ exchanger, Zn^<2+>/H^+ exchanger, metal-binding protein, proton pumps in the vacuolar membranes in this project.(1) Cation/H^+ exchangers: Rice has five isoforms of cation/H^+ exchanger (CAX). CAX1a among five isoforms is expressed in all tissues examined and is highly expressed in companion and endodermis cells, which has high concentration of Ca^<2+>. We estimate that CAX1a functions to reserve Ca^<2+> into vacuoles and is involved in the Ca^<2+> detoxification.(2) Novel metal binding protein (PCaP1): We found a novel metal cation-binding protein, AtPCaP1, in Arabidopsis thaliana. The protein is N-myristoylated and stably associated with the plasma membrane in vitro and in vivo. AtPCaP1 binds to Ca^<2+>, Cu^<2+>, Ca^<2+>/calmodulin complex, and phosphatidylinositol phosphates. From these biochemical properties, we estimate that the protein is involved in signal transduction of environmental stresses, such as metal and pathogen stresses.(3) Vacuolar zinc transporter (MTP1): Arabidopsis MTP1 has been demonstrated to be located to the vacuolar membrane. The knockout mutant of MTP1 was highly sensitive to high concentrations (more than 0.2 mM) of zinc. Thus, MTP1 might be involved in the Zn detoxification by transport of the excess Zn^<2+> ion in the cytoplasm into vacuoles. By heterologous expression of MTP1 in yeast and direct measurement of zinc transport using Zn-65, we demonstrated that MTP1 functions as Zn^<2+>/H^+ exchanger. Furthermore, we found that the cytoplasmic histidine-rich region functions as a buffering pocket of Zn2+ and a sensor of the zinc level at the cytoplasmic surface.(4) Vacuolar proton pump: Vacuolar membrane H^+-pyrophosphatase (H^+-PPase) acidifies vacuoles and maintains the pH gradient across the membrane. We determined the essential residues and functional motifs in the enzyme.

本课题在液泡膜Ca^2+/H^+交换体、Zn^2+/H^+交换体、金属结合蛋白、质子泵等方面取得了以下研究结果。(1)阳离子/H^+交换剂：水稻有五种阳离子/H^+交换剂（CAX）。CAX 1a在所有组织中均有表达，在伴皮层和内皮细胞中表达最高，且伴皮层和内皮细胞中Ca 2+浓度较高。我们估计CAX 1a的功能是将Ca^<2+>储存到液泡中，并参与Ca^<2+>解毒。(2)新型金属结合蛋白（PCaP 1）：我们在拟南芥中发现了一种新型金属阳离子结合蛋白AtPCaP 1。该蛋白是N-肉豆蔻酰化的，在体外和体内与质膜稳定结合。AtPCaP 1与Ca^2+、Cu^2+、Ca^2+/钙调蛋白复合物和磷脂酰肌醇磷酸结合。从这些生化特性，我们估计，该蛋白质参与的信号转导的环境压力，如金属和病原体的压力。(3)液泡膜锌转运蛋白1（MTP 1）：拟南芥MTP 1已被证明定位于液泡膜。MTP 1的敲除突变体对高浓度（大于0.2 mM）的锌高度敏感。因此，MTP 1可能通过将细胞质中过量的Zn^<2+>离子转运到液泡中而参与锌的解毒过程。通过在酵母中异源表达MTP 1并使用Zn-65直接测量锌转运，我们证明了MTP 1作为Zn^<2+>/H^+交换剂的功能。此外，我们发现，胞质组氨酸丰富的区域功能作为缓冲口袋的Zn 2+和传感器的锌水平在细胞质表面。(4)质子泵：质子膜H^+-焦磷酸酶（H^+-PPase）酸化液泡并维持跨膜的pH梯度。我们确定了酶中的必需残基和功能基序。