Nitrate and nitrite are transported by different specific transport systems and by a bispecific transporter in Chlamydomonas reinhardtii
Nitrate and nitrite are transported by different specific transport systems and by a bispecific transporter in Chlamydomonas reinhardtii
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DOI：
10.1074/jbc.271.4.2088
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发表时间：
1996-01-26
影响因子：
4.8
通讯作者：
Fernandez, E
中科院分区：
文献类型：
--
作者：
Galvan, A;Quesada, A;Fernandez, E
来自莱茵衣藻的硝酸盐转运突变体和用含有C.莱茵衣藻nar 2/Nrt 2;1或nar 2/Nrt 2;2基因已用于研究硝酸盐和亚硝酸盐转运系统。缺乏硝酸盐同化簇基因的突变体表现出高亲和力的亚硝酸盐转运活性（系统3），这是受到铵抑制，似乎是独立的功能nar 2基因。携带nar 2/Nrt 2;2的转化体恢复了高亲和力的硝酸盐转运体活性（系统2），并显示出亚硝酸盐转运活性，其性质与非转化细胞中的亚硝酸盐转运活性相似。携带nar 2/Nrt 2;1的转化体恢复了高亲和力硝酸盐转运体活性（系统1）以及显著增强的亚硝酸盐转运活性。亚硝酸盐运输介导的系统1是非常敏感的抑制μ M浓度的硝酸盐。结果表明，三个与硝酸盐同化相关的高亲和力转运系统在C.莱茵哈迪：一种特异于亚硝酸根，第二种由nar 2/Nrt 2;2编码，特异于硝酸根，另一种由nar 2/Nrt 2;1编码，其对这两种阴离子是双特异性的。
Nitrate transport mutants from Chlamydomonas reinhardtii and strains derived from them upon transformation with plasmids containing the C. reinhardtii nar2/Nrt2;1 or nar2/Nrt2;2 genes have been used to study nitrate and nitrite transport systems. Mutants lacking nitrate assimilation clustered genes showed a high affinity nitrite transporter activity (system 3), which was subject to ammonium inhibition and appeared to be independent of a functional nar2 gene. Transformants carrying nar2/Nrt2;2 recovered a high affinity nitrate transporter activity (system 2) and showed nitrite transport activities with properties similar 60 those in nontransformed cells. Transformants carrying nar2/Nrt2;1 recovered high affinity nitrate transporter activity (system 1) together with a considerably enhanced nitrite transport activity. Nitrite transport mediated by system 1 was very sensitive to inhibition by nitrate at mu M concentrations. Results strongly suggest that three nitrate assimilation related high affinity transport systems operate in C. reinhardtii: one specific for nitrite, a second one encoded by nar2/Nrt2;2 specific for nitrate, and another one encoded by nar2/Nrt2;1, which is bispecific for these two anions.