糖转运蛋白(STPs)是高亲和力H+偶联的己糖转运体。最近,STP13对多种植物物种的细菌和真菌病原体抗性的贡献已经引起了极大的兴趣。来源叶的定量PCR分析,发育中的胚胎,菜豆(普通豆)的种皮表明,在整个种子发育过程中,PvSTP13.1在源叶和种皮中表达。相比之下,在发育中的胚胎中检测到极低水平的PvSTP13.1转录本。为了表征传输机制,PvSTP13.1在非洲爪狼卵母细胞中表达,使用双电极电压钳制分析了向内电流。PvSTP13.1显示出作为H偶联的单糖转运体的功能,在去极化的膜电位下对己糖和醛固酮具有独特的高亲和力。具体来说,在评估的31种基质中,其中包括己醛糖,脱氧己糖,果糖,3-O-甲基-D-葡萄糖,醛固酮,多元醇糖苷,二糖,三糖,和葡萄糖醛酸,PvSTP13.1对葡萄糖(43μM)表现出最高的亲和力(K0.5),甘露糖(92μM),半乳糖(145μM),果糖(224μM),木糖(1.0mM),和岩藻糖(3.7mM)在pH5.6,去极化膜电位为-40mV。此处显示的结果表明,PvSTP13.1有助于从源叶片和发育中种子的外皮中的外质空间中回收己糖。
Sugar transport proteins (STPs) are high-affinity H+-coupled hexose symporters. Recently, the contribution of STP13 to bacterial and fungal pathogen resistance across multiple plant species has garnered significant interest. Quantitative PCR analysis of source leaves, developing embryos, and seed coats of Phaseolus vulgaris L. (common bean) revealed that PvSTP13.1 was expressed in source leaves and seed coats throughout seed development. In contrast, PvSTP13.1 transcripts were detected at exceedingly low levels in developing embryos. To characterize the transport mechanism, PvSTP13.1 was expressed in Xenopus laevis oocytes, and inward-directed currents were analyzed using two-electrode voltage clamping. PvSTP13.1 was shown to function as an H+-coupled monosaccharide symporter exhibiting a unique high affinity for hexoses and aldopentoses at depolarized membrane potentials. Specifically, of the 31 assessed substrates, which included aldohexoses, deoxyhexoses, fructose, 3-O-methyl-D-glucose, aldopentoses, polyols, glycosides, disaccharides, trisaccharides, and glucuronic acid, PvSTP13.1 displayed the highest affinity (K 0.5) for glucose (43 μM), mannose (92 μM), galactose (145 μM), fructose (224 μM), xylose (1.0 mM), and fucose (3.7 mM) at pH 5.6 at a depolarized membrane potential of -40 mV. The results presented here suggest PvSTP13.1 contributes to retrieval of hexoses from the apoplasmic space in source leaves and coats of developing seeds.