Rottenberg H, Koeppe R E
Department of Pathology, Hahnemann University, Philadelphia, Pennsylvania 19102.
Biochemistry. 1989 May 16;28(10):4361-7. doi: 10.1021/bi00436a036.
Gramicidin and the truncated derivatives desformylgramicidin (desfor) and des(formylvalyl)gramicidin (desval) stimulate monovalent cation transport in rat liver mitochondria. Cation fluxes were compared indirectly from the effect of cations on the membrane potential at steady state (state 4) or from the associated stimulation of electron transport. Rb+ transport was measured directly from the uptake of 86Rb. The truncated gramicidins show enhanced selectivity for K+ and Rb+ when compared to gramicidin. Moreover, the pattern of selectivity within the alkali cation series is altered, i.e., Rb+ greater than K+ greater than Cs+ greater than Na+ greater than Li+ for desfor and desval as compared to Cs+ greater than Rb+ greater than K+ = Na+ greater than Li+ for gramicidin. The cation fluxes through the truncated derivatives are more strongly dependent on the cation concentration. The presence of high concentrations of permeating cation enhances the transport of other cations through the truncated derivative channels, suggesting that cations are required for stabilizing the channel structure. In high concentrations of KCl, desfor and desval are nearly as effective as gramicidin in collapsing the mitochondrial membrane potential, and, consequently, in the uncoupling of oxidative phosphorylation and enhancement of ATP hydrolysis. Preliminary experiments with liposomes show that 86Rb exchange is stimulated by desfor and desval almost to the same extent as gramicidin. These results strongly suggest that the truncated gramicidins form a novel conducting channel which differs from the gramicidin head-to-head, single-stranded beta 6.3-helical dimer ("channel") in its conductance characteristic and its structure.(ABSTRACT TRUNCATED AT 250 WORDS)
短杆菌肽以及截短衍生物去甲酰短杆菌肽（去甲酰）和去（甲酰缬氨酰）短杆菌肽（去缬氨酰）可刺激大鼠肝线粒体中的单价阳离子转运。通过阳离子对稳态（状态4）膜电位的影响或相关的电子传递刺激来间接比较阳离子通量。通过86Rb的摄取直接测量Rb+转运。与短杆菌肽相比，截短的短杆菌肽对K+和Rb+表现出更高的选择性。此外，碱金属阳离子系列中的选择性模式发生了改变，即去甲酰短杆菌肽和去缬氨酰短杆菌肽的选择性模式为Rb+＞K+＞Cs+＞Na+＞Li+，而短杆菌肽的为Cs+＞Rb+＞K+ = Na+＞Li+。通过截短衍生物的阳离子通量对阳离子浓度的依赖性更强。高浓度渗透阳离子的存在增强了其他阳离子通过截短衍生物通道的转运，这表明阳离子对于稳定通道结构是必需的。在高浓度KCl中，去甲酰短杆菌肽和去缬氨酰短杆菌肽在消除线粒体膜电位方面几乎与短杆菌肽一样有效，因此，在氧化磷酸化解偶联和ATP水解增强方面也一样有效。用脂质体进行的初步实验表明，去甲酰短杆菌肽和去缬氨酰短杆菌肽对86Rb交换的刺激程度几乎与短杆菌肽相同。这些结果强烈表明，截短的短杆菌肽形成了一种新型导电通道，其电导率特性和结构不同于短杆菌肽头对头、单链β6.3螺旋二聚体（“通道”）。（摘要截短至250字）
