Subunits act independently in a cyclic nucleotide-activated K(+) channel.
Ion channels gated by cyclic nucleotides have crucial roles in neuronal excitability and signal transduction of sensory neurons. Here, we studied ligand binding of a cyclic nucleotide-activated K(+) channel from Mesorhizobium loti and its isolated cyclic nucleotide-binding domain. The channel and the binding domain alone bind cyclic AMP with similar affinity in a non-cooperative manner. The cAMP sensitivities of binding and activation coincide. Thus, each subunit in the tetrameric channel acts independently of the others. The binding and gating properties of the bacterial channel are distinctively different from those of eukaryotic cyclic nucleotide-gated channels.
Institut für Neurowissenschaften und Biophysik INB-1, Abteilung Zelluläre Biophysik, Forschungszentrum Jülich, Leo-Brandt-Strasse, 52425 Jülich, Germany.
Abhishek
A
Cukkemane
Bärbel
B
Grüter
Kerstin
K
Novak
Thomas
T
Gensch
Wolfgang
W
Bönigk
Tanja
T
Gerharz
U Benjamin
UB
Kaupp
Reinhard
R
Seifert
D020561:Alphaproteobacteria / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D000242:Cyclic AMP / Q000737:chemistry*; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000737:chemistry* / Q000235:genetics; D008024:Ligands; D015221:Potassium Channels / Q000737:chemistry* / Q000235:genetics; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry; D013050:Spectrometry, Fluorescence
D001426:Bacterial Proteins; D054815:Cyclic Nucleotide-Gated Cation Channels; D008024:Ligands; D015221:Potassium Channels; D021122:Protein Subunits; D000242:Cyclic AMP