Sun I L, Crane F L, Grebing C, Löw H
J Bioenerg Biomembr. 1984 Dec;16(5-6):583-95. doi: 10.1007/BF00743247.
A transmembrane electron transport system has been studied in HeLa cells using an external impermeable oxidant, ferricyanide. Reduction of ferricyanide by HeLa cells shows biphasic kinetics with a rate up to 500 nmoles/min/g w.w. (wet weight) for the fast phase and half of this rate for the slow phase. The apparent Km is 0.125 mM for the fast rate and 0.24 mM for the slow rate. The rate of reduction is proportional to cell concentration. Inhibition of the rate by glycolysis inhibitors indicates the reduction is dependent on glycolysis, which contributes the cytoplasmic electron donor NADH. Ferricyanide reduction is shown to take place on the outside of cells for it is affected by external pH and agents which react with the external surface. Ferricyanide reduction is accompanied by proton release from the cells. For each mole of ferricyanide reduced, 2.3 moles of protons are released. It is, therefore, concluded that a transmembrane redox system in HeLa cells is coupled to proton gradient generation across the membrane. We propose that this redox system may be an energy source for control of membrane function in HeLa cells. The promotion of cell growth by ferricyanide (0.33-0.1 mM), which can partially replace serum as a growth factor, strongly supports this hypothesis.
利用一种外部不可渗透的氧化剂铁氰化物，在HeLa细胞中研究了一种跨膜电子传输系统。HeLa细胞对铁氰化物的还原呈现双相动力学，快速相速率高达500纳摩尔/分钟/克湿重，慢速相速率为快速相的一半。快速速率的表观Km为0.125毫摩尔，慢速速率的表观Km为0.24毫摩尔。还原速率与细胞浓度成正比。糖酵解抑制剂对速率的抑制表明还原依赖于糖酵解，糖酵解提供细胞质电子供体NADH。铁氰化物的还原发生在细胞外部，因为它受外部pH值和与细胞外表面反应的试剂影响。铁氰化物的还原伴随着质子从细胞中释放。每还原1摩尔铁氰化物，释放2.3摩尔质子。因此，得出结论，HeLa细胞中的跨膜氧化还原系统与跨膜质子梯度的产生相偶联。我们提出，这种氧化还原系统可能是HeLa细胞中控制膜功能的能量来源。铁氰化物（0.33 - 0.1毫摩尔）可部分替代血清作为生长因子促进细胞生长，这有力地支持了这一假说。
