Lee S H, Sutherland T O, Deveś R, Brodie A F
Proc Natl Acad Sci U S A. 1980 Jan;77(1):102-6. doi: 10.1073/pnas.77.1.102.
Irradiation of the inverted membrane vesicles of Mycobacterium phlei with light at 360 nm inactivated the natural menaquinone [MK(9)(II-H)] and resulted in a loss of substrate oxidation, pH gradient, membrane potential, active transport of proline or calcium ions, and oxidative phosphorylation. Restoration of the protonmotive force and active transport occurred on addition of naphthoquinones such as vitamin K(1), menadione, or lapachol to the irradiated membrane vesicles. However, coupled phosphorylation was restored only by vitamin K(1). Menadione and lapachol did not act as uncoupling agents. The magnitude of the pH gradient and membrane potential in the quinone-restored system was a reflection of the rate of oxidation and was correlated with the rate of uptake of proline or Ca(2+). These results are consistent with the chemosmotic hypothesis proposed for the energy transducing mechanism for active transport and further demonstrate that the complete respiratory chain is not required to drive active transport. In contrast, the data suggest that in addition to the driving force (protonmotive force) necessary to establish oxidative phosphorylation, a specific spatial orientation of the respiratory components, such as the naphthaquinones, is essential for the utilization of the proton gradient or membrane potential or both. Bypass of electrons from the respiratory chain with menadione may explain the inability of this quinone to restore oxidative phosphorylation; however, lapachol restores oxidation by the same electron transport pathway as the natural menaquinone but fails to restore phosphorylation. Because all three quinones restore the protonmotive force, other factors that are discussed must be considered in understanding the mechanism of oxidative phosphorylation.
用360nm的光照射草分枝杆菌的反向膜泡会使天然甲萘醌[MK(9)(II-H)]失活，并导致底物氧化、pH梯度、膜电位、脯氨酸或钙离子的主动转运以及氧化磷酸化的丧失。向受照射的膜泡中添加萘醌类物质，如维生素K(1)、甲萘醌或拉帕醇后，质子动力和主动转运得以恢复。然而，只有维生素K(1)能恢复偶联磷酸化。甲萘醌和拉帕醇不起解偶联剂的作用。醌恢复系统中pH梯度和膜电位的大小反映了氧化速率，并与脯氨酸或Ca(2+)的摄取速率相关。这些结果与为主动转运的能量转换机制提出的化学渗透假说一致，并进一步证明驱动主动转运不需要完整的呼吸链。相比之下，数据表明，除了建立氧化磷酸化所需的驱动力（质子动力）外，呼吸成分（如萘醌）的特定空间取向对于质子梯度或膜电位或两者的利用至关重要。甲萘醌使电子从呼吸链旁路，这可能解释了这种醌无法恢复氧化磷酸化的原因；然而，拉帕醇通过与天然甲萘醌相同的电子传递途径恢复氧化，但无法恢复磷酸化。由于所有三种醌都能恢复质子动力，在理解氧化磷酸化机制时必须考虑所讨论的其他因素。
