Vandorpe D H, Small D L, Dabrowski A R, Morris C E
Department of Biology, University of Ottawa, Ontario, Canada.
Biophys J. 1994 Jan;66(1):46-58. doi: 10.1016/S0006-3495(94)80749-0.
The long-standing distinction between channels and transporters is becoming blurred, with one pump protein even able to convert reversibly to a channel in response to osmotic shock. In this light, it is plausible that stretch channels, membrane proteins whose physiological roles have been elusive, may be transporters exhibiting channel-like properties in response to mechanical stress. We recently described a case, however, where this seems an unlikely explanation. An Aplysia K channel whose physiological pedigree is well established (it is an excitability-modulating conductance mechanism) was found able to be activated by stretch. Here we establish more firmly the identity of this Aplysia conductance, the S-channel, as a stretch channel. We show that the permeation and fast kinetic properties of the stretch-activated channel and of the FMRFamide-activated S-channel are indistinguishable. We have also made progress in extending the kinetic analysis of the stretch channel to situations of multiple channel activity. This analysis implements a novel renewal theory approach and is therefore explained in some detail.
通道蛋白和转运蛋白之间长期存在的区别正变得模糊，甚至有一种泵蛋白能够在渗透压休克的刺激下可逆地转变为通道蛋白。据此推测，拉伸通道（一种生理功能一直难以捉摸的膜蛋白）可能是在机械应力作用下表现出类似通道特性的转运蛋白。然而，我们最近描述了一个案例，这个解释似乎不太可能成立。一种生理谱系明确的海兔钾通道（它是一种调节兴奋性的电导机制）被发现能够被拉伸激活。在此，我们更确切地确定了这种海兔电导（即S通道）作为拉伸通道的身份。我们表明，拉伸激活通道和FMRF酰胺激活的S通道的通透和快速动力学特性难以区分。我们在将拉伸通道的动力学分析扩展到多通道活动的情况方面也取得了进展。这种分析采用了一种新颖的更新理论方法，因此将进行详细解释。
