Differential localizations and functions of rice nucleotide pyrophosphatase/phosphodiesterase isozymes 1 and 3
Differential localizations and functions of rice nucleotide pyrophosphatase/phosphodiesterase isozymes 1 and 3
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DOI：
10.5511/plantbiotechnology.10.1228a
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发表时间：
2011-01-01
影响因子：
1.6
通讯作者：
Mitsui, Toshiaki
中科院分区：
文献类型：
--
作者：
Kaneko, Kentaro;Yamada, Chie;Mitsui, Toshiaki
我们先前的研究表明，在水稻细胞中，ADP-葡萄糖水解核苷酸焦磷酸酶/磷酸二酯酶（NPP）1通过分泌途径从内质网（ER）-高尔基体系统转运到质体[Nanjo等人（2006）Plant Cell 18：2582-2592]。本研究分析了其同工酶NPP 3的酶学特性和亚细胞定位。与NPP 1不同，NPP 3对ADP-葡萄糖没有水解活性，也没有质体靶向能力。此外，它们形成成熟酶蛋白的N-末端蛋白水解加工方案之间存在明显差异。NPP 1通过两步蛋白水解加工成熟为70-kDa蛋白。我们检测到的72 kDa形式的NPP 1在水稻细胞的微粒体中，除了70 kDa的成熟蛋白，强烈表明，前蛋白加工发生后，在ER-高尔基体系统。为了阐明NPP 1的质体靶向信号的存在，在水稻细胞中检测了一系列羧基端截短的与绿色荧光蛋白融合的NPP 1蛋白的质体定位。结果表明，NPP 1不能通过N-末端区域（包括ER信号序列和前蛋白加工位点）转运到质体，而308 - 478个氨基酸残基的肽段可能是NPP 1转运到质体的重要区域。
Our previous investigation demonstrated that ADP-glucose hydrolytic nucleotide pyrophosphatase/phosphodiesterase (NPP) 1 is transported from the endoplasmic reticulum (ER)-Golgi system to the plastids via a secretory pathway in rice cells [Nanjo et al. (2006) Plant Cell 18: 2582-2592]. In this study, we analyzed the enzymatic characteristics and subcellular localization of its isozyme, NPP3. Unlike NPP1, NPP3 exhibited no hydrolytic activity toward ADP-glucose and no plastid-targeting ability. Furthermore, there was a clear difference between their N-terminal proteolytic processing schemes to form mature enzyme proteins. NPP1 is matured to a 70-kDa protein by two-step proteolytic processing. We detected the 72 kDa form of NPP1 in the microsomes of rice cells in addition to the 70 kDa mature protein, strongly suggesting that proprotein processing occurs post-translationally in the ER-Golgi system. To clarify the existence of the plastid-targeting signal of NPP1, the plastid localization of a series of carboxy-terminal truncated NPP1 proteins fused with green fluorescence protein was tested in rice cells. The results showed that NPP1 cannot be delivered to the plastid by the N-terminal region, including the ER signal sequence and the proprotein processing site, and that the peptide region, from 308 to 478 amino acid residues, is probably important for the transport of NPP1 into plastids in rice cells.