Kato Keita, Shitan Nobukazu, Shoji Tsubasa, Hashimoto Takashi
Graduate School of Biological Sciences, Nara Institute of Science and Technology, Takayama 8916-5, Ikoma, Nara 630-0192, Japan.
Kobe Pharmaceutical University, Motoyama Kitamachi 4-19-1, Higashinada, Kobe, Hyogo 658-8558, Japan.
Phytochemistry. 2015 May;113:33-40. doi: 10.1016/j.phytochem.2014.05.011. Epub 2014 Jun 16.
The purine permeases (PUPs) constitute a large plasma membrane-localized transporter family in plants that mediates the proton-coupled uptake of nucleotide bases and their derivatives, such as adenine, cytokinins, and caffeine. A Nicotiana tabacum (tobacco) PUP-family transporter, nicotine uptake permease 1 (NtNUP1), was previously shown to transport tobacco alkaloids and to affect both nicotine biosynthesis and root growth in tobacco plants. Since Arabidopsis PUP1, which belongs to the same subclade as NtNUP1, was recently reported to transport pyridoxine and its derivatives (vitamin B6), it was of interest to examine whether NtNUP1 could also transport these substrates. Direct uptake measurements in the yeast Saccharomyces cerevisiae demonstrated that NtNUP1 efficiently promoted the uptake of pyridoxamine, pyridoxine, anatabine, and nicotine. The naturally occurring (S)-isomer of nicotine was preferentially transported over the (R)-isomer. Transport studies using tobacco BY-2 cell lines overexpressing NtNUP1 or PUP1 showed that NtNUP1, similar to PUP1, transported various compounds containing a pyridine ring, but that the two transporters had distinct substrate preferences. Therefore, the previously reported effects of NtNUP1 on tobacco physiology might involve bioactive metabolites other than tobacco alkaloids.
嘌呤通透酶（PUPs）在植物中构成了一个位于质膜上的大型转运蛋白家族，介导质子偶联的核苷酸碱基及其衍生物（如腺嘌呤、细胞分裂素和咖啡因）的摄取。先前已证明一种烟草（Nicotiana tabacum）PUP家族转运蛋白——尼古丁摄取通透酶1（NtNUP1）可转运烟草生物碱，并影响烟草植株中尼古丁的生物合成和根系生长。由于拟南芥PUP1与NtNUP1属于同一亚分支，最近有报道称其可转运吡哆醇及其衍生物（维生素B6），因此研究NtNUP1是否也能转运这些底物很有意义。在酿酒酵母中的直接摄取测量表明，NtNUP1能有效促进吡哆胺、吡哆醇、降烟碱和尼古丁的摄取。尼古丁的天然（S）-异构体比（R）-异构体更易被转运。使用过表达NtNUP1或PUP1的烟草BY-2细胞系进行的转运研究表明，与PUP1类似，NtNUP1可转运各种含吡啶环的化合物，但这两种转运蛋白具有不同的底物偏好。因此，先前报道的NtNUP1对烟草生理学的影响可能涉及除烟草生物碱之外的生物活性代谢物。
