Molecular template for a voltage sensor in a novel K+ channel. II. Conservation of a eukaryotic sensor fold in a prokaryotic K+ channel.
KvLm, a novel bacterial depolarization-activated K(+) (Kv) channel isolated from the genome of Listeria monocytogenes, contains a voltage sensor module whose sequence deviates considerably from the consensus sequence of a Kv channel sensor in that only three out of eight conserved charged positions are present. Surprisingly, KvLm exhibits the steep dependence of the open channel probability on membrane potential that is characteristic of eukaryotic Kv channels whose sensor sequence approximates the consensus. Here we asked if the KvLm sensor shared a similar fold to that of Shaker, the archetypal eukaryotic Kv channel, by examining if interactions between conserved residues in Shaker known to mediate sensor biogenesis and function were conserved in KvLm. To this end, each of the five non-conserved residues in the KvLm sensor were mutated to their Shaker-like charged residues, and the impact of these mutations on the voltage dependence of activation was assayed by current recordings from excised membrane patches of Escherichia coli spheroplasts expressing the KvLm mutants. Conservation of pairwise interactions was investigated by comparison of the effect of single mutations to the impact of double mutations presumed to restore wild-type fold and voltage sensitivity. We observed significant functional coupling between sites known to interact in Shaker Kv channels, supporting the notion that the KvLm sensor largely retains the fold of its eukaryotic homologue.
Lundby
Alicia
A
Section of Neurobiology, Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA.
Santos
Jose S
JS
Zazueta
Cecilia
C
Montal
Mauricio
M
D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D002462:Cell Membrane / Q000502:physiology; D017124:Conserved Sequence; D006860:Hydrogen Bonding; D015640:Ion Channel Gating / Q000502:physiology*; D008969:Molecular Sequence Data; D009154:Mutation; D015221:Potassium Channels / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D016415:Sequence Alignment; D051637:Shaker Superfamily of Potassium Channels / Q000737:chemistry* / Q000235:genetics / Q000502:physiology
D001426:Bacterial Proteins; D015221:Potassium Channels; D051637:Shaker Superfamily of Potassium Channels; C107790:prokaryotic potassium channel