4-Aminobutyrate (GABA) transporters from the amine-polyamine-choline superfamily:: substrate specificity and ligand recognition profile of the 4-aminobutyrate permease from Bacillus subtilis
4-Aminobutyrate (GABA) transporters from the amine-polyamine-choline superfamily:: substrate specificity and ligand recognition profile of the 4-aminobutyrate permease from Bacillus subtilis
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DOI：
10.1042/bj3330565
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发表时间：
1998-08-01
影响因子：
4.1
通讯作者：
King, SC
中科院分区：
文献类型：
--
作者：
Brechtel, CE;King, SC
先前的一项研究[Ferson，Wray和Fisher(1996)Mel.微生物。22,693-701]已经表明，转座子介导的与大肠杆菌GABA(II-氨基丁酸盐)转运蛋白47%相同的蛋白质的破坏取消了氮限制培养条件诱导枯草芽孢杆菌表达GABA转运蛋白活性的能力。这直接证明了枯草杆菌GABA通透酶(Gabp)基因可以弥补gabp阴性的大肠杆菌株的转运缺陷。出乎意料的是，枯草杆菌GabP的配基识别图谱被发现与高度同源的E.ColiGabP的配基识别图谱有很大不同。与大肠杆菌GabP不同，枯草芽孢杆菌GabP：(I)表现出约对3-碳(β-丙氨酸，K-m=9.6µM)和4-碳(GABA，K-m=37µM)氨基酸具有同等的偏好，并且(Ii)抵抗笨重、构象受限的化合物(例如，胡椒酸、古瓦卡因)的抑制，这些化合物对大脑中的GABA转运体具有活性。本研究还表明，枯草杆菌GabP可以通过与[H-3]GABA的逆流将几种开链GABA类似物(3-氨基丁酸酯、3-氨基丙酸酯、顺式-4-氨基丁烯酸)跨膜转运。因此，与枯草杆菌GabP的配体识别结构域不如来自大肠杆菌的紧密同源物的想法一致，前者对底物识别和转位表现出比后者更严格的要求。大肠杆菌和枯草杆菌GABA转运蛋白的这些不同的功能特征为识别胺-多胺-胆碱转运蛋白超家族中的配体识别结构域提供了基础。
A previous study [Ferson, Wray and Fisher (1996) Mel. Microbiol. 22, 693-701] has shown that transposon-mediated disruption of a protein 47 % identical to the Escherichia coli GABA (ii-aminobutyrate) transporter abolishes the ability of nitrogen-limited culture conditions to induce expression of a GABA transport activity in Bacillus subtilis. Here it is demonstrated directly that the B. subtilis GABA permease (gabP) gene can complement the transport defect in the gabP-negative E. coli strain. Unexpectedly, the ligand-recognition profile of the B. subtilis GabP was found to differ substantially from that of the highly homologous E. coli GabP. Unlike the E. coli GabP, the B. subtilis GabP: (i) exhibits approx. equal preference for the 3-carbon (beta-alanine, K-m = 9.6 mu M) and the 4-carbon (GABA, K-m = 37 mu M) amino acids, and (ii) resists inhibition by bulky, conformationally constrained compounds (e.g. nipecotic acid, guvacine), which are active against GABA transporters from brain. The present study shows additionally that the B. subtilis GabP can translocate several open-chain GABA analogues (3-aminobutyrate, 3-aminopropanoate, cis-4-aminobutenoate) across the membrane via counterflow against [H-3]GABA. Thus, consistent with the idea that the ligand-recognition domain of the B. subtilis GabP is less spacious than that of the close homologue from E. coli, the former exhibits more stringent requirements than the latter for substrate recognition and translocation. These distinct functional characteristics of the E. coli and B. subtilis GABA transporters provide a basis by which to identify ligand-recognition domains within the amine-polyamine-choline transporter superfamily.