Induction of conductance heterogeneity in gramicidin channels.
Induction of conductance heterogeneity in gramicidin channels.
复制标题
短杆菌肽通道中电导异质性的诱导。
DOI：
10.1021/bi00442a007
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发表时间：
1989
期刊：
影响因子：
2.9
通讯作者：
Andersen,OS
中科院分区：
文献类型：
--
作者：
Sawyer,DB;Koeppe2nd,RE;Andersen,OS
摘要：在我们实验室以前的工作中，5-10%由[Val 1]短杆菌肽A形成的通道的电导落在传统上定义的标准短杆菌肽通道的窄范围之外[例如，参见Russell et al.（1986）Biophys. J. 49，673]。然而，来自其他实验室的报告显示，高达50%的[瓦尔]短杆菌肽通道具有落在标准通道范围之外的电导[例如，参见Prasad et al.（1986）Biochemistry 25，456]。短杆菌肽单通道电导分布的这种实验室间变化表明电导变体是由一些环境因素诱导的[Busath埃塔尔（1987）生物物理学。J. 51，79]。为了测试外源性试剂是否可以诱导这种电导异质性，我们研究了非离子或两性离子去污剂对短杆菌肽通道行为的影响。在磷脂双分子层中，洗涤剂的加入诱导短杆菌肽通道行为的许多变化：所有测试的洗涤剂增加通道的出现率和平均持续时间;大多数洗涤剂降低标准通道的电导;和所有洗涤剂，但一个增加电导异质性。这些结果表明，电导异质性可能是由环境扰动引起的，从而为短杆菌肽通道异质性的实验室间差异提供了可能的解释。此外，不同的去污剂效应表明可能的机制，去污剂可以诱导构象扰动，导致短杆菌肽单通道电导的变化。理解膜蛋白功能的一个重要问题是蛋白质的功能如何依赖于其所在的膜环境。这是一个难以解决的问题，在研究中的人口的膜蛋白，居住在一个有时相当不好控制的天然脂质环境。然而，平面脂质双层中跨膜通道的单通道研究允许详细研究脂质环境调节的功能后果。单通道实验对于研究膜蛋白之间可能的异质性问题特别有用，因为单通道实验根据定义研究的是单个分子，
Revised Manuscript Received May 4, 1989 abstract: In previous work from our laboratory, 5-10% of thechannels formed by [Val1] gramicidin A have conductances that fall outside the narrow range that conventionally has defined the standard gramicidin channel [eg, see Russell et al.(1986) Biophys. J. 49, 673], Reports from other laboratories, however, show that up to 50% of [Val'Jgramicidin channels have conductances that fall outside the range for standard channels [eg, see Prasad et al.(1986) Biochemistry 25, 456]. This laboratory-to-laboratory variation in the distribution of gramicidin single-channel conductances suggests that the conductance variants are induced by some environmental factor (s)[Busath etal.(1987) Biophys. J. 51, 79]. In order to test whether extrinsic agents can induce such conductance heterogeneity, we examined the effects of nonionic or zwitterionic detergents upon gramicidin channel behavior. In phospholipid bilayers, detergent addition induces many changes in gramicidin channel behavior: all detergents tested increase the channel appearance rate and average duration; most detergents decrease the conductance of the standard channel; and all but one of the detergents increase the conductance heterogeneity. These results show that the conductance heterogeneity can result from environmental perturbations, thus providing a possible explanationfor the laboratory-to-laboratory variation in the heterogeneity of gramicidin channels. In addition, the differential detergenteffects suggest possible mechanismsby which detergents can induce the conformational perturbations that result in gramicidin single-channel conductance variations..^^. n important problem pertaining to understanding mem-brane protein function is how function depends on the mem-brane environment in which a protein resides. This is a difficult problem toaddress in studies on populations of mem-brane proteins that reside within a sometimes rather poorly controlled native lipid environment. Single-channel studies on membrane-spanning channels in planar lipid bilayers, however, allow the functional consequences of lipid environment modulations to be studiedin detail. Single-channel experiments are particularly useful to examine questions pertaining to the possible heterogeneity among membrane proteins, because one by definition studies single molecular