甘薯蔗糖转运蛋白IbSUT1x在酵母细胞中的定位

Localization of IbSUT1x Protein from Ipomoea batatas (L.) Lam in Yeast Cells

蔗糖转运蛋白是植物特有的一类载体蛋白,酿酒酵母突变株SUSY7/ura3常被利用来研究蔗糖转运蛋白的功能,但在研究中发现,有的蔗糖转运蛋白在酵母中未表现出蔗糖转运的功能.但这或许并不是其实际功能的体现,而是由于这类蛋白无法准确定位到酵母的细胞膜上造成的.IbSUT1x是本实验室从甘薯中分离到的一个蔗糖转运蛋白基因,但是在SUSY7/ura3中未表现出明显的蔗糖转运功能.本研究通过用激光共聚焦显微镜对IbSUT1x与绿色荧光蛋白(Green fluorescent protein,GFP)的融合蛋白的表达和定位的观察,发现IbSUT1x不仅在酵母细胞中有表达,而且表达的蛋白质定位在酵母的细胞膜上.结果表明,IbSUT1x在酵母细胞中不能转运蔗糖,该蛋白很可能不具有蔗糖转运功能,或者其与蔗糖的亲和力很低.

Sucrose transporters（SUTs）,or termed as sucrose carriers（SUCs）,only exist in plants and play important roles in long-distance transport of photosynthate through phloem from source organs to sink ones.Its function was always studied with yeast（Saccharomyces cerevisiae） strain SUSY7/ura3 which is usually used as a model for sucrose uptake activity research.Researchers found that some sucrose transporters could not transport sucrose,which might be on account of the failed localization（not target to plasma membrane） in yeast cells.IbSUT1x is a sucrose transporter gene isolated from sweet potato（Ipomoea batatas）,and it does not display apparent sucrose uptake activity.In the present study,it was revealed that IbSUT1x could be successfully targeted to plasma membrane of yeast cells by the localization of IbSUT1x-green fluorescent protein（GFP） fusion protein using laser scanning confocal microscopy.The result suggestes that IbSUT1x can not load sucrose into yeast cells,or just has low sucrose affinity.