A superfamily of voltage-gated sodium channels in bacteria.
NaChBac, a six-alpha-helical transmembrane-spanning protein cloned from Bacillus halodurans, is the first functionally characterized bacterial voltage-gated Na(+)-selective channel. As a highly expressing ion channel protein, NaChBac is an ideal candidate for high resolution structural determination and structure-function studies. The biological role of NaChBac, however, is still unknown. In this report, another 11 structurally related bacterial proteins are described. Two of these functionally expressed as voltage-dependent Na(+) channels (Na(V)PZ from Paracoccus zeaxanthinifaciens and Na(V)SP from Silicibacter pomeroyi). Na(V)PZ and Na(V)SP share approximately 40% amino acid sequence identity with NaChBac. When expressed in mammalian cell lines, both Na(V)PZ and Na(V)SP were Na(+)-selective and voltage-dependent. However, their kinetics and voltage dependence differ significantly. These single six-alpha-helical transmembrane-spanning subunits constitute a widely distributed superfamily (Na(V)Bac) of channels in bacteria, implying a fundamental prokaryotic function. The degree of sequence homology (22-54%) is optimal for future comparisons of Na(V)Bac structure and function of similarity and dissimilarity among Na(V)Bac proteins. Thus, the Na(V)Bac superfamily is fertile ground for crystallographic, electrophysiological, and microbiological studies.
Koishi
Ryuta
R
Howard Hughes Medical Institute, Department of Cardiovascular Research, Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
Xu
Haoxing
H
Ren
Dejian
D
Navarro
Betsy
B
Spiller
Benjamin W
BW
Shi
Qing
Q
Clapham
David E
DE
D000595:Amino Acid Sequence; D001407:Bacillus / Q000502:physiology*; D001426:Bacterial Proteins / Q000032:analysis / Q000302:isolation & purification / Q000502:physiology*; D003001:Cloning, Molecular; D004594:Electrophysiology; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D017421:Sequence Analysis; D015222:Sodium Channels / Q000032:analysis / Q000302:isolation & purification / Q000502:physiology*
D001426:Bacterial Proteins; D015222:Sodium Channels