Hirschi K D, Zhen R G, Cunningham K W, Rea P A, Fink G R
Whitehead Institute for Biomedical Research, Nine Cambridge Center, MA 02142, USA.
Proc Natl Acad Sci U S A. 1996 Aug 6;93(16):8782-6. doi: 10.1073/pnas.93.16.8782.
Reestablishment of the resting state after stimulus-coupled elevations of cytosolic-free Ca2+ requires the rapid removal of Ca2+ from the cytosol of plant cells. Here we describe the isolation of two genes, CAX1 and CAX2, from Arabidopsis thaliana that suppress a mutant of Saccharomyces cerevisiae that has a defect in vacuolar Ca2+ accumulation. Both genes encode polypeptides showing sequence similarities to microbial H+/Ca2+ antiporters. Experiments on vacuolar membrane-enriched vesicles isolated from yeast expressing CAX1 or CAX2 demonstrate that these genes encode high efficiency and low efficiency H+/Ca2+ exchangers, respectively. The properties of the CAX1 gene product indicate that it is the high capacity transporter responsible for maintaining low cytosolic-free Ca2+ concentrations in plant cells by catalyzing pH gradient-energized vacuolar Ca2+ accumulation.
在由刺激引起的胞质游离Ca2+浓度升高后，恢复静息状态需要将Ca2+迅速从植物细胞的胞质中移除。在此，我们描述了从拟南芥中分离出的两个基因CAX1和CAX2，它们可抑制酿酒酵母中一个液泡Ca2+积累存在缺陷的突变体。这两个基因编码的多肽与微生物H+/Ca2+反向转运体具有序列相似性。对从表达CAX1或CAX2的酵母中分离出的富含液泡膜的囊泡进行的实验表明，这些基因分别编码高效和低效的H+/Ca2+交换体。CAX1基因产物的特性表明，它是一种高容量转运体，通过催化由pH梯度驱动的液泡Ca2+积累，负责维持植物细胞中低水平的胞质游离Ca2+浓度。
