Furuichi T, Cunningham K W, Muto S
Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan.
Plant Cell Physiol. 2001 Sep;42(9):900-5. doi: 10.1093/pcp/pce145.
The gene encoding voltage-gated channel with high affinity for Ca(2+) permeation has not been cloned from plants. In the present study, we isolated a full-length cDNA encoding a putative Ca(2+ )channel (AtTPC1) from Arabidopsis. AtTPC1 has two conserved homologous domains, both of which contain six transmembrane segments (S1-S6) and a pore loop (P) between S5 and S6 in each domain, and has the highest homology with the two pore channel TPC1 recently cloned from rat. The overall structure is similar to the half of the general structure of alpha-subunits of voltage-activated Ca(2+) channels from animals. AtTPC1 rescued the Ca(2+) uptake activity of a yeast mutant cch1. Sucrose-induced luminescence, which reflects a cytosolic free Ca(2+) increase in aequorin-expressing Arabidopsis leaves, was enhanced by overexpression of AtTPC1 and suppressed by antisense expression of it. Sucrose-H(+) symporters AtSUC1 and 2, which depolarize membrane potential of cells receiving sucrose, also depressed a Ca(2+) increase by their antisense expression. These results suggest that AtTPC1 mediates a voltage-activated Ca(2+ )influx in Arabidopsis leaf cells.
对Ca(2+)通透具有高亲和力的电压门控通道编码基因尚未从植物中克隆出来。在本研究中，我们从拟南芥中分离出一个编码假定Ca(2+)通道（AtTPC1）的全长cDNA。AtTPC1有两个保守的同源结构域，每个结构域都包含六个跨膜片段（S1-S6）以及S5和S6之间的一个孔环（P），并且与最近从大鼠中克隆出的双孔通道TPC1具有最高的同源性。其整体结构类似于动物电压激活Ca(2+)通道α亚基一般结构的一半。AtTPC1挽救了酵母突变体cch1的Ca(2+)摄取活性。蔗糖诱导的发光反映了表达水母发光蛋白的拟南芥叶片中胞质游离Ca(2+)的增加，AtTPC1的过表达增强了这种发光，而其反义表达则抑制了这种发光。蔗糖-H(+)同向转运体AtSUC1和2可使接收蔗糖的细胞的膜电位去极化，它们的反义表达也抑制了Ca(2+)的增加。这些结果表明，AtTPC1介导了拟南芥叶细胞中电压激活的Ca(2+)内流。
