大肠杆菌中在没有 NhaB 钠氢反向转运蛋白的情况下能够利用丝氨酸生长的重组细胞的特性。
Properties of recombinant cells capable of growing on serine without NhaB Na+/H+ antiporter in Escherichia coli.
作者信息
Kayahara T, Thelen P, Ogawa W, Inaba K, Tsuda M, Goldberg E B, Tsuchiya T
机构信息
Department of Microbiology, Faculty of Pharmaceutical Sciences, Okayama University, Japan.
出版信息
J Bacteriol. 1992 Nov;174(22):7482-5. doi: 10.1128/jb.174.22.7482-7485.1992.
Escherichia coli HIT-1 has a mutation in the Na+/H+ antiporter gene, nhaB (P. Thelen, T. Tsuchiya, and E. B. Goldberg, J. Bacteriol. 173:6553-6557, 1991). This strain is not able to utilize serine as a carbon source (T. Ishikawa, H. Hama, M. Tsuda, and T. Tsuchiya, J. Biol. Chem. 262:7443-7446, 1987), because an active NhaB is required to maintain the electrochemical potential of Na+, which drives serine transport via the Na+/serine carrier, the major transport system for serine. We isolated recombinant cells from a cross between strains HIT-1 and Hfr, and these cells were able to grow on serine even though the NhaB Na+/H+ antiporter of the recombinant cells was still defective. We found that the activity of the H+/serine cotransport system, one of the minor serine transport systems in E. coli, was elevated in the recombinant cells. H+/serine cotransport activity was induced by leucine in the recombinant cells more strongly than in strain HIT-1. A kinetic analysis showed that the Vmax, but not the Km, of the transport system was much higher in the recombinant cells than in strain HIT-1 cells.
大肠杆菌HIT-1的Na⁺/H⁺逆向转运蛋白基因nhaB发生了突变（P. 特伦、T. 土屋和E. B. 戈德堡，《细菌学杂志》173:6553 - 6557, 1991年）。该菌株无法利用丝氨酸作为碳源（T. 石川、H. 滨、M. 津田和T. 土屋，《生物化学杂志》262:7443 - 7446, 1987年），因为需要有活性的NhaB来维持Na⁺的电化学势，而Na⁺的电化学势驱动丝氨酸通过Na⁺/丝氨酸载体进行转运，丝氨酸载体是丝氨酸的主要转运系统。我们从HIT-1菌株和高频重组菌株（Hfr）的杂交后代中分离出重组细胞，这些细胞能够在丝氨酸上生长，尽管重组细胞的NhaB Na⁺/H⁺逆向转运蛋白仍然存在缺陷。我们发现，大肠杆菌中丝氨酸次要转运系统之一的H⁺/丝氨酸共转运系统在重组细胞中的活性有所提高。与HIT-1菌株相比，重组细胞中亮氨酸对H⁺/丝氨酸共转运活性的诱导作用更强。动力学分析表明，该转运系统的最大反应速度（Vmax）而非米氏常数（Km）在重组细胞中比在HIT-1菌株细胞中要高得多。
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