加拿大和美国科学家联合研究小组开发出一种应用荧光光谱技术观察研究单个膜蛋白运动的新方法。膜蛋白的主要功能是控制细胞与其周边环境的离子交换。专家认为,该项研究成果有助于人们增强对离子通道的认识和了解。相关研究文章发表在最新出版的《美国国家科学院院报》上。
离子通道类似于一台小型纳米机器或纳米阀门,如果这些微小阀门运转失灵,将引发人体肌肉、中枢神经系统和心脏等发生各种遗传疾病。
与照相机的光圈原理相似,这些膜蛋白通过开启和关闭动作来控制细胞与其周边环境的离子交换运动,这种离子交换运动促成了沿着我们神经细胞的电信号的传输。这些细微阀门的尺寸大约是人眼瞳孔大小的百万分之一。加美科学家所采用的新技术可测量到单离子通道,并可研究离子通道内部不同部分之间如何进行信息沟通。
由加拿大蒙特利尔大学物理系教授里卡德·布朗克牵头的联合小组对基于4个同样的亚单元建立的钾离子通道进行了研究,这种钾离子通道形成了可以穿过膜的微细小孔,小孔能够打开和关闭以开通或阻断离子传导。
科学家使用新开发出的荧光光谱技术,区分出4个亚单元,首次实现了对4个亚单元的运动分别进行跟踪研究。他们发现,4个亚单元分子是协同发挥作用的,从而解释了为何在电生理学实验中没有在电流中发现中间级。该项研究成果解决了在该领域存在的长期争论:一个钾离子的4个亚单元究竟是各自独立发挥作用还是协同发挥作用。
布朗克博士表示,该项发现有助于增强人们对离子通道的认识和了解。其重要性在于,膜蛋白在人体中发挥着重要的作用,而且其基因突变会引发许多严重的遗传疾病,也因此它们是重要的药物标靶。(生物谷Bioon.com)
生物谷推荐原始出处:
PNAS December 11, 2008, doi: 10.1073/pnas.0807056106
Fluorescence detection of the movement of single KcsA subunits reveals cooperativity
Rikard Bluncka,1, Hugo McGuirea, H. Clark Hydeb, and Francisco Bezanillab
aDépartement de Physique and GéPROM, Université de Montréal, Montréal, QC, Canada H3C 3J7; and
bDepartment of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637
The prokaryotic KcsA channel is gated at the helical bundle crossing by intracellular protons and inactivates at the extracellular selectivity filter. The C-terminal transmembrane helix has to undergo a conformational change for potassium ions to access the central cavity. Whereas a partial opening of the tetrameric channel is suggested to be responsible for subconductance levels of ion channels, including KcsA, a cooperative opening of the 4 subunits is postulated as the final opening step. In this study, we used single-channel fluorescence spectroscopy of KcsA to directly observe the movement of each subunit and the temporal correlation between subunits. Purified KcsA channels labeled at the C terminus near the bundle crossing have been inserted into supported lipid bilayer, and the fluorescence traces analyzed by means of a cooperative or independent Markov model. The analysis revealed that the 4 subunits do not move fully independently but instead showed a certain degree of cooperativity. However, the 4 subunits do not simply open in 1 concerted step.