Abe K, Ruan Z S, Maloney P C
Department of Physiology, Johns Hopkins Medical School, Baltimore, Maryland 21205, USA.
J Biol Chem. 1996 Mar 22;271(12):6789-93. doi: 10.1074/jbc.271.12.6789.
OxlT is the oxalate/formate exchange protein that represents the vectorial component of a proton-motive metabolic cycle in Oxalobacter formigenes. Here we report the cloning and sequencing of OxlT and describe its expression in Escherichia coli. The OxlT amino acid sequence specifies a polytopic hydrophobic protein of 418 residues with a mass of 44,128 daltons. Analysis of hydropathy and consideration of the distribution of charged residues suggests an OxlT secondary structure having 12 transmembrane segments, oriented so that the N and C termini face the cytoplasm. Expression of OxlT in E. coli coincides with appearance of a capacity to carry out the self-exchange of oxalate and the heterologous, electrogenic exchange of oxalate with formate. The unusually high velocity of OxlT-mediated transport is also preserved in E. coli. We conclude that the essential features of OxlT are retained on its expression in E. coli.
OxlT是草酸/甲酸交换蛋白，它代表了产甲酸草酸杆菌质子动力代谢循环的矢量成分。在此，我们报告了OxlT的克隆和测序，并描述了其在大肠杆菌中的表达。OxlT氨基酸序列确定了一个由418个残基组成的多跨膜疏水蛋白，质量为44,128道尔顿。对亲水性的分析以及对带电残基分布的考虑表明，OxlT二级结构具有12个跨膜片段，其取向使得N端和C端面向细胞质。OxlT在大肠杆菌中的表达与进行草酸自身交换以及草酸与甲酸的异源、电致交换的能力的出现相一致。OxlT介导的转运的异常高速度在大肠杆菌中也得以保留。我们得出结论，OxlT的基本特征在其于大肠杆菌中的表达中得以保留。
