Functional and physiological characterization of the Arabidopsis monosaccharide-transporter-like proteins At1g05030, At1g67300 and At1g79820 from endomembranes

拟南芥有一个由单糖转运蛋白（MST）和MST样转运蛋白（MSTL）组成的大家族（超过50个成员），可分为7个明显可区分的亚群。预测所有这些蛋白都有12个跨膜螺旋。超过50%的这些蛋白质在我们的小组中被表征，并被证明可以催化不同的己糖，或线性或环状多元醇穿过质膜或穿过不同细胞类型的细胞质的运输。这7个亚群中只有4个蛋白，其中一个亚群含有一个定位于质体的蛋白（At5g16150; AtpGlcT）和一个定位于高尔基体的蛋白（At1g79820; SGB1）。在该项目中，我们计划研究该亚群中剩余的两个尚未表征的蛋白，At1g05030和At1g67300。在初步分析中，我们可以证明这些蛋白是高尔基蛋白（At1g05030）或tono质体定位蛋白（At1g67300）。此外，我们可以证明At1g67300和已经发表的高尔基定位转运蛋白At1g79820 （SGB1）存在更短的、可选择性剪接的mrna。这些较短的mrna编码的蛋白质只有6个tm -螺旋，这在之前研究的MSTL超家族的任何蛋白质中都没有观察到。我们的目标是对At1g05030和At1g67300 （12 TM）基因编码的蛋白质进行功能和生理表征，并阐明由At1g67300和At1g79820 （6 TM）的短转录本编码的蛋白质的作用。

Arabidopsis has a large family (more than 50 members) of monosaccharide transporters (MST) and MST-like (MSTL) transporters that fall into 7 clearly distinguishable subgroups. All of these proteins are predicted to have 12 transmembrane (TM) helices. More than 50% of these proteins were characterized in our group and shown to catalyze the transport of different hexoses, or linear or cyclic polyols across the plasma membranes or across the tonoplast of different cell types. One of these seven subgroups with only four proteins contains one protein that localizes to plastids (At5g16150; AtpGlcT) and one protein that localizes to the Golgi (At1g79820; SGB1). In the proposed project we plan to study the two remaining, yet uncharacterized proteins of this subgroup, At1g05030 and At1g67300. In preliminary analyses we could show that these proteins are Golgi- (At1g05030) or tonoplast-localized (At1g67300). Moreover, we could demonstrate the existence of shorter, alternatively spliced mRNAs for At1g67300 and for the already published Golgi-localized transporter At1g79820 (SGB1). These shorter mRNAs encode proteins with only 6 TM-helices that were not observed for any of the previously studied proteins of the MSTL superfamily. We aim to functionally and physiologically characterize the proteins encoded by the At1g05030 and At1g67300 (12 TM) genes and to elucidate the role of the proteins encoded by the shorter transcripts of At1g67300 and At1g79820 (6 TM).