Three amino acids in the C-linker are major determinants of gating in cyclic nucleotide-gated channels.
The activation of cyclic nucleotide-gated (CNG) channels is a complex process comprising the initial ligand binding and a consecutive allosteric transition from a closed to an open configuration. The cone and olfactory CNG channels differ considerably in cyclic nucleotide affinity and efficacy. In each channel, the cyclic nucleotide-binding site is connected to the last transmembrane segment of the channel by a linker peptide (C-linker) of approximately 90 amino acids. Here we report that replacement of three amino acids in the cone C-linker by the corresponding amino acids of the olfactory channel (I439V, D481A and D494S) profoundly enhanced the cAMP efficacy and increased the affinities for cAMP and cGMP. Unlike the wild-type cone channel, the mutated channel exhibited similar single-channel kinetics for both cGMP and cAMP, explaining the increase in cAMP efficacy. We thus conclude that the identified amino acids are major determinants of channel gating.
Zong
X
X
Institut für Pharmakologie und Toxikologie, Technische Universität München, Germany.
Zucker
H
H
Hofmann
F
F
Biel
M
M
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D000818:Animals; D002417:Cattle; D002460:Cell Line; D000242:Cyclic AMP / Q000494:pharmacology; D006152:Cyclic GMP / Q000494:pharmacology; D054815:Cyclic Nucleotide-Gated Cation Channels; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects; D007473:Ion Channels / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D011817:Rabbits
D000596:Amino Acids; D054815:Cyclic Nucleotide-Gated Cation Channels; D007473:Ion Channels; D010446:Peptide Fragments; D000242:Cyclic AMP; D006152:Cyclic GMP