Bénitah J P, Ranjan R, Yamagishi T, Janecki M, Tomaselli G F, Marban E
Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Biophys J. 1997 Aug;73(2):603-13. doi: 10.1016/S0006-3495(97)78096-2.
The pores of ion channel proteins are often modeled as static structures. In this view, selectivity reflects rigidly constrained backbone orientations. Such a picture is at variance with the generalization that biological proteins are flexible, capable of major internal motions on biologically relevant time scales. We tested for motions in the sodium channel pore by systematically introducing pairs of cysteine residues throughout the pore-lining segments. Two distinct pairs of residues spontaneously formed disulfide bonds bridging domains I and II. Nine other permutations, involving all four domains, were capable of disulfide bonding in the presence of a redox catalyst. The results are inconsistent with a single fixed backbone structure for the pore; instead, the segments that line the permeation pathway appear capable of sizable motions.
离子通道蛋白的孔道通常被模拟为静态结构。按照这种观点，选择性反映了刚性受限的主链取向。这样的描述与生物学蛋白质具有柔韧性、能够在生物学相关的时间尺度上进行主要内部运动的普遍观点不一致。我们通过在整个孔道内衬片段中系统地引入半胱氨酸残基对来测试钠通道孔道中的运动。两对不同的残基自发形成了连接结构域I和II的二硫键。另外九种涉及所有四个结构域的排列在氧化还原催化剂存在的情况下能够形成二硫键。结果与孔道单一固定的主链结构不一致；相反，构成渗透途径内衬的片段似乎能够进行相当大的运动。
