Hoshino T, Kose K, Uratani Y
Laboratory of Molecular Cellular Biology, Mitsubishi Kasei Institute of Life Sciences, Tokyo, Japan.
Mol Gen Genet. 1990 Feb;220(3):461-7. doi: 10.1007/BF00391754.
The gene braB, encoding the Na(+)-coupled carrier for branched-chain amino acids in Pseudomonas aeruginosa PAO, was cloned on cosmid pMMB34. The cosmid clones carrying the braB gene were identified as those that restored growth at low leucine concentration and Na(+)-dependent leucine transport activity to P. aeruginosa PAO3536 defective in the transport of branched-chain amino acids. Determination of the nucleotide sequence of the DNA fragment shows that the braB gene comprises 1311 bp and encodes a hydrophobic protein of 437 amino acids with a calculated Mr of 45,279. The hydropathy profile suggests that there exist in the carrier protein 12 hydrophobic segments long enough to traverse the membrane. The amino acid sequence shows a high degree of homology with the brnQ product, a branched-chain amino acid carrier of Salmonella typhimurium, while no homology in the nucleotide sequences is found in the braB and brnQ genes.
编码铜绿假单胞菌PAO中支链氨基酸的Na⁺偶联载体的braB基因，被克隆到黏粒pMMB34上。携带braB基因的黏粒克隆被鉴定为那些能恢复在低亮氨酸浓度下生长以及对支链氨基酸转运有缺陷的铜绿假单胞菌PAO3536的Na⁺依赖性亮氨酸转运活性的克隆。对该DNA片段核苷酸序列的测定表明，braB基因由1311个碱基对组成，编码一个437个氨基酸的疏水蛋白，计算的分子量为45279。亲水性图谱表明，载体蛋白中存在12个足够长以穿越膜的疏水片段。氨基酸序列与鼠伤寒沙门氏菌的支链氨基酸载体brnQ产物具有高度同源性，而在braB和brnQ基因的核苷酸序列中未发现同源性。
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