André B, Hein C, Grenson M, Jauniaux J C
Laboratoire de Physiologie Cellulaire et de Génétique des Levures, Université Libre de Bruxelles, Belgium.
Mol Gen Genet. 1993 Feb;237(1-2):17-25. doi: 10.1007/BF00282779.
Transport of 4-aminobutyric acid (GABA) in Saccharomyces cerevisiae is mediated by three transport systems: the general amino acid permease (GAP1 gene), the proline permease (PUT4 gene), and a specific GABA permease (UGA4 gene) which is induced in the presence of GABA. The UGA4 gene encoding the inducible GABA-specific transporter was cloned and sequenced and its expression analyzed. The predicted amino acid sequence shows that UGA4 encodes a 62 kDa protein having 9-12 putative membrane-spanning regions. The predicted UGA4 protein shares significant sequence similarity with the yeast choline transporter (CTR gene), exhibiting but limited similarity to the previously reported GABA transporters, i.e. the yeast GAP1 and PUT4 permeases and the rat brain GAT-1 transporter. Induction of UGA4 in the presence of GABA is exerted at the level of UGA4 mRNA accumulation, most probably at the level of transcription itself. This induction is conferred by the 5' flanking region and requires the integrity of two positive regulatory proteins, the inducer-specific factor UGA3 and the pleiotropic factor UGA35/DURL/DAL81. In the absence of the pleiotropic UGA43/DAL80 repressor, UGA4 is constitutively expressed at high level.
酿酒酵母中4-氨基丁酸（GABA）的转运由三种转运系统介导：通用氨基酸通透酶（GAP1基因）、脯氨酸通透酶（PUT4基因）和一种在GABA存在时被诱导的特异性GABA通透酶（UGA4基因）。对编码可诱导GABA特异性转运蛋白的UGA4基因进行了克隆、测序并分析了其表达情况。预测的氨基酸序列表明，UGA4编码一种62 kDa的蛋白质，具有9 - 12个推定的跨膜区域。预测的UGA4蛋白与酵母胆碱转运蛋白（CTR基因）具有显著的序列相似性，但与先前报道的GABA转运蛋白，即酵母GAP1和PUT4通透酶以及大鼠脑GAT - 1转运蛋白的相似性有限。在GABA存在时UGA4的诱导作用发生在UGA4 mRNA积累水平，很可能发生在转录本身的水平。这种诱导作用由5'侧翼区域赋予，并且需要两种正向调节蛋白的完整性，即诱导物特异性因子UGA3和多效性因子UGA35/DURL/DAL81。在缺乏多效性UGA43/DAL80阻遏物的情况下，UGA4会持续高水平表达。
