Bradbeer C, Woodrow M L
J Bacteriol. 1976 Oct;128(1):99-104. doi: 10.1128/jb.128.1.99-104.1976.
This paper presents some evidence that the osmotic shock-sensitive, energy-dependent transfer of vitamin B12 from outer membrane receptor sites into the interior of cells of Escherichia coli requires an energized inner membrane, without obligatory intermediation of adenosine 5'-triphosphate (ATP). The experiments measured the effects of glucose, D-lactate, anaerobiosis, arsenate, cyanide, and 2,4-dinitrophenol upon the rates of B12 transport by starved cells of E. coli KBT001, which possesses a functional Ca2+, Mg2+-stimulated adenosine triphosphatase (Ca,MgATPase), and of E. coli AN120, which lacks this enzyme. Both strains were able to utilize glucose and D-lactate aerobically to potentiate B12 transport, indicating that the Ca,MgATPase was not essential for this process. When respiratory electron transport was blocked, either by cyanide or by anaerobic conditions, and the primary source of energy for the cells was presumably ATP from glucose fermentation, the rate of B12 transport was much reduced in E. coli AN120 but not in E.coli KBT001. These results support the view that the CaMgATPase can play a role in B12 transport but only when the energy for this process must be derived from ATP. The results of experiments with arsenate also supported the conclusion that the generation of phosphate bond energy was not absolutely required for B12 transport.
本文提供了一些证据，表明维生素B12从外膜受体位点向大肠杆菌细胞内部的渗透休克敏感、能量依赖型转运需要有活力的内膜，而无需腺苷5'-三磷酸（ATP）的强制介导。实验测量了葡萄糖、D-乳酸、厌氧状态、砷酸盐、氰化物和2,4-二硝基苯酚对大肠杆菌KBT001（具有功能性Ca2+、Mg2+刺激的腺苷三磷酸酶（Ca,MgATPase））和大肠杆菌AN120（缺乏这种酶）的饥饿细胞中B12转运速率的影响。两种菌株都能够有氧利用葡萄糖和D-乳酸来增强B12转运，这表明Ca,MgATPase对于此过程并非必不可少。当呼吸电子传递被氰化物或厌氧条件阻断，且细胞的主要能量来源大概是葡萄糖发酵产生的ATP时，大肠杆菌AN120中B12的转运速率大幅降低，而大肠杆菌KBT001中则没有。这些结果支持了这样一种观点，即CaMgATPase可以在B12转运中发挥作用，但仅在此过程的能量必须来自ATP时才起作用。用砷酸盐进行的实验结果也支持了这一结论，即B12转运并非绝对需要磷酸键能量的产生。
