期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2011
卷号：108
期号：30
页码：12313-12318
DOI：10.1073/pnas.1106811108
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Many voltage-gated ion channel (VGIC) superfamily members contain six-transmembrane segments in which the first four form a voltage-sensing domain (VSD) and the last two form the pore domain (PD). Studies of potassium channels from the VGIC superfamily together with identification of voltage-sensor only proteins have suggested that the VSD and the PD can fold independently. Whether such transmembrane modularity is common to other VGIC superfamily members has remained untested. Here we show, using protein dissection, that the Silicibacter pomeroyi voltage-gated sodium channel (NaVSp1) PD forms a stand-alone, ion selective pore (NaVSp1p) that is tetrameric, -helical, and that forms functional, sodium-selective channels when reconstituted into lipid bilayers. Mutation of the NaVSp1p selectivity filter from LESWSM to LDDWSD, a change similar to that previously shown to alter ion selectivity of the bacterial sodium channel NaVBh1 (NaChBac), creates a calcium-selective pore-only channel, CaVSp1p. We further show that production of PDs can be generalized by making pore-only proteins from two other extremophile NaVs: one from the hydrocarbon degrader Alcanivorax borkumensis (NaVAb1p), and one from the arsenite oxidizer Alkalilimnicola ehrlichei (NaVAe1p). Together, our data establish a family of active pore-only ion channels that should be excellent model systems for study of the factors that govern both sodium and calcium selectivity and permeability. Further, our findings suggest that similar dissection approaches may be applicable to a wide range of VGICs and, thus, serve as a means to simplify and accelerate biophysical, structural, and drug development efforts.
