Molecular mechanism and regulation of development of vacuoles during elongation of plant cells.

在高等植物的细胞中，液泡具有储存细胞器、水解室和胀压控制者的功能。液泡的空间填充作用对植物细胞的生长也很重要。细胞体积的增加是由液泡的增大引起的。因此，如果不充分了解液泡的生物发生和发育，就不可能讨论细胞的生长。本研究研究了液泡H^+- atp酶和H^+-焦磷酸酶作为液泡膜的标记物。这两个质子泵将质子输送到液泡中并维持液泡的酸度。绿豆液泡H^+- atp酶由9个亚基组成，而H^+-焦磷酸酶由一个73000道尔顿的多肽组成。得到了以下结果：(1)在绿藻、苔藓和蕨类植物中均检测到液泡atp酶和H^+-焦磷酸酶。焦磷酸酶的分子质量和分子活性与绿豆酶相似。(2)细胞成熟后空泡膜中焦磷酸酶的含量下降，而atp酶的含量保持不变。因此，atp酶和H^+-焦磷酸酶的合成调控机制可能不同。(3)在液泡膜中发现了一个疏水性强的主要积分蛋白（VM23）。从氨基末端序列和对DCCD（二环己基碳二亚胺）等抑制剂的反应性数据来看，VM23被认为是一个水通道或离子转运体。

In the cells of higher plants, vacuoles function as storage organelles, as hydrolytic compartments, and as controllers of turgor pressure. The space-filling role of the vacuoles is also important and is essential to the growth of plant cells. The increase in cell volume is accounted for by enlargement of the vacuole. Thus it is impossible to discuss the cell growth without a full understanding of the biogenesis and development of vacuoles. In this study, the vacuolar H^+-ATPase and H^+-pyrophosphatase were investigated as markers of the vacuolar membranes. These two proton pumps transport protons into vacuoles and maintain their acidity.Vacuolar H^+-ATPase of mung bean consists of nine subunits, while the H^+-pyrophosphatase consists of a single polypeptide of 73,000 daltons. The following results have been obtained.(1) The vacuolar ATPase and H^+-pyrophosphatase were detected in all plant species investigated including green alga, moss and fern. The molecular masses and molecular activities of the pyrophosphatase were similar to the mung bean enzyme.(2) The content of the pyrophosphatase in the vacuolar membrane decreased after maturation of cells, although the amount of the ATPase was constant. Therefore, the regulatory mechanisms of synthesis may be different between the ATPase and H^+-pyrophosphatase.(3) A major integral protein (VM23) which is very hydrophobic was found in vacuolar membrane. From the data concerning the amino- terminal sequence and reactivity to inhibitor such as DCCD (dicylohexylcarbodiimide), VM23 has been estimated as a water channel or ion transporter.