Structural, Biochemical, and Functional Characterization of the Cyclic Nucleotide Binding Homology Domain from the Mouse EAG1 Potassium Channel
- Authors
- Marques-Carvalho, M.J., Sahoo, N., Muskett, F.W., Vieira-Pires, R.S., Gabant, G., Cadene, M., Schönherr, R., and Morais-Cabral, J.H.
- ID
- ZDB-PUB-120705-5
- Date
- 2012
- Source
- Journal of molecular biology 423(1): 34-46 (Journal)
- Registered Authors
- Keywords
- CNB domain, CNB-homology domain, calmodulin, crystal structure
- MeSH Terms
-
- Animals
- Binding Sites
- Crystallography, X-Ray
- Ether-A-Go-Go Potassium Channels/chemistry*
- Ether-A-Go-Go Potassium Channels/metabolism
- Mice
- Nucleotides, Cyclic/chemistry*
- Potassium/metabolism
- Protein Structure, Tertiary
- PubMed
- 22732247 Full text @ J. Mol. Biol.
KCNH channels are voltage-gated potassium channels with important physiological functions. In these channels, a C-terminal cytoplasmic region, known as the cyclic nucleotide binding homology (CNB-homology) domain displays strong sequence similarity to cyclic nucleotide binding (CNB) domains. However, the isolated domain does not bind cyclic nucleotides. Here, we report the X-ray structure of the CNB-homology domain from the mouse EAG1 channel. Through comparison with the recently determined structure of the CNB-homology domain from the zebrafish ELK (eaglike K+) channel and the CNB domains from the MlotiK1 and HCN (hyperpolarizationactivated cyclic nucleotidegated) potassium channels, we establish the structural features of CNB-homology domains that explain the low affinity for cyclic nucleotides. Our structure establishes that the “self-liganded” conformation, where two residues of the C-terminus of the domain are bound in an equivalent position to cyclic nucleotides in CNB domains, is a conserved feature of CNB-homology domains. Importantly, we provide biochemical evidence that suggests that there is also an unliganded conformation where the C-terminus of the domain peels away from its bound position. A functional characterization of this unliganded conformation reveals a role of the CNB-homology domain in channel gating.