The cation selectivity filter of the bacterial sodium channel, NaChBac.
The Bacillus halodurans voltage-gated sodium-selective channel (NaChBac) (Ren, D., B. Navarro, H. Xu, L. Yue, Q. Shi, and D.E. Clapham. 2001b. SCIENCE: 294:2372-2375), is an ideal candidate for high resolution structural studies because it can be expressed in mammalian cells and its functional properties studied in detail. It has the added advantage of being a single six transmembrane (6TM) orthologue of a single repeat of mammalian voltage-gated Ca(2+) (Ca(V)) and Na(+) (Na(V)) channels. Here we report that six amino acids in the pore domain (LESWAS) participate in the selectivity filter. Replacing the amino acid residues adjacent to glutamatic acid (E) by a negatively charged aspartate (D; LEDWAS) converted the Na(+)-selective NaChBac to a Ca(2+)- and Na(+)-permeant channel. When additional aspartates were incorporated (LDDWAD), the mutant channel resulted in a highly expressing voltage-gated Ca(2+)-selective conductance.
Yue
Lixia
L
Howard Hughes Medical Institute, Children's Hospital, Boston, MA 02115, USA.
Navarro
Betsy
B
Ren
Dejian
D
Ramos
Arnolt
A
Clapham
David E
DE
D000595:Amino Acid Sequence; D000818:Animals; D001407:Bacillus / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D001426:Bacterial Proteins; D016466:CHO Cells; D019556:COS Cells; D002118:Calcium / Q000494:pharmacology / Q000502:physiology*; D002412:Cations / Q000494:pharmacology; D002522:Chlorocebus aethiops; D006224:Cricetinae; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008969:Molecular Sequence Data; D009154:Mutation / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D015222:Sodium Channels / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*
D001426:Bacterial Proteins; D002412:Cations; C443666:NaChBac protein, bacteria; D015222:Sodium Channels; D002118:Calcium