title: Voltage-gated sodium channel (NaV) protein dissection creates a set of functional pore-only proteins.
abstract: 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 (Na(V)Sp1) PD forms a stand-alone, ion selective pore (Na(V)Sp1p) that is tetrameric, α-helical, and that forms functional, sodium-selective channels when reconstituted into lipid bilayers. Mutation of the Na(V)Sp1p selectivity filter from LESWSM to LDDWSD, a change similar to that previously shown to alter ion selectivity of the bacterial sodium channel Na(V)Bh1 (NaChBac), creates a calcium-selective pore-only channel, Ca(V)Sp1p. We further show that production of PDs can be generalized by making pore-only proteins from two other extremophile Na(V)s: one from the hydrocarbon degrader Alcanivorax borkumensis (Na(V)Ab1p), and one from the arsenite oxidizer Alkalilimnicola ehrlichei (Na(V)Ae1p). 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.
authors: Department of Biochemistry, University of California, San Francisco, CA 94158-9001, USA.
authors: David
authors: D
authors: Shaya
authors: Mohamed
authors: M
authors: Kreir
authors: Rebecca A
authors: RA
authors: Robbins
authors: Stephanie
authors: S
authors: Wong
authors: Justus
authors: J
authors: Hammon
authors: Andrea
authors: A
authors: Brüggemann
authors: Daniel L
authors: DL
authors: Minor
mesh_terms: D053521:Alcanivoraceae / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D055592:Biophysical Phenomena; D042001:Ectothiorhodospiraceae / Q000235:genetics / Q000378:metabolism; D055724:Electrophysiological Phenomena; D008969:Molecular Sequence Data; D009154:Mutation; D010802:Phylogeny; D017510:Protein Folding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D041902:Rhodobacteraceae / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015222:Sodium Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D015222:Sodium Channels