Yamaguchi A, Ohmori H, Kaneko-Ohdera M, Nomura T, Sawai T
Division of Microbial Chemistry, Faculty of Pharmaceutical Sciences, Chiba University, Japan.
Antimicrob Agents Chemother. 1991 Jan;35(1):53-6. doi: 10.1128/AAC.35.1.53.
The effects of ionophores on tetracycline accumulation in Escherichia coli cells were investigated in the presence of polymyxin B nonapeptide. Accumulation was inhibited by nigericin but not by valinomycin. Tetracycline accumulation was stimulated by decreasing the pH of the medium and inhibited by the addition of magnesium ions. These results indicated that tetracycline enters cells through diffusion as a protonated form (TH2) and is accumulated as a membrane-impermeable magnesium-tetracycline chelate complex (THMg+). This noncarrier diffusion hypothesis was confirmed by the fact that tetracycline accumulated in protein-free liposomes through an artificially imposed pH difference.
在多粘菌素B九肽存在的情况下，研究了离子载体对大肠杆菌细胞中四环素积累的影响。尼日利亚菌素抑制积累，而缬氨霉素则无此作用。降低培养基的pH值可刺激四环素的积累，而添加镁离子则抑制其积累。这些结果表明，四环素以质子化形式（TH2）通过扩散进入细胞，并以膜不可渗透的镁 - 四环素螯合物复合物（THMg+）形式积累。四环素通过人为施加的pH差异在无蛋白脂质体中积累这一事实证实了这种非载体扩散假说。
