title: Two distinct calcium-calmodulin interactions with N-terminal regions of the olfactory and rod cyclic nucleotide-gated channels characterized by NMR spectroscopy.
abstract: The interactions of calcium-calmodulin with two fragments of the N-terminal domains of the olfactory alpha-subunit and rod beta-subunit cyclic nucleotide-gated channels have been investigated using nuclear magnetic resonance spectroscopy. The results indicate that in the two cases both the N-terminal and the C-terminal calmodulin lobes are involved in the interaction. The olfactory cyclic nucleotide-gated channel segment forms a 1:1 complex with calmodulin, whereas the rod fragment forms a 2:1 complex. The correlation times of the two complexes, as estimated by (15)N relaxation studies, are compatible with the observed stoichiometries. These results indicate differences in the mode of action by which calmodulin modulates the activity of both channels, and suggest either that the rod channel is modulated through a simultaneous interaction of two beta-subunits with calmodulin or that other regions of the N-terminus are necessarily implicated in the binding.
authors.affiliation: Department of Chemical Sciences and Technologies, University of Rome 'Tor Vergata', via della Ricerca Scientifica, 00133, Rome, Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: Orsale
authors.forename: Sonia
authors.initials: S
authors.lastname: Melino
authors.forename: Gian Marco
authors.initials: GM
authors.lastname: Contessa
authors.forename: Vincent
authors.initials: V
authors.lastname: Torre
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Andreotti
authors.forename: Andrea
authors.initials: A
authors.lastname: Motta
authors.forename: Maurizio
authors.initials: M
authors.lastname: Paci
authors.forename: Alessandro
authors.initials: A
authors.lastname: Desideri
authors.forename: Daniel O
authors.initials: DO
authors.lastname: Cicero
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000737:chemistry / Q000378:metabolism*; D002147:Calmodulin / Q000737:chemistry / Q000378:metabolism*; D054815:Cyclic Nucleotide-Gated Cation Channels; D007473:Ion Channels / Q000737:chemistry / Q000378:metabolism*; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D009830:Olfactory Bulb / Q000737:chemistry; D011485:Protein Binding; D021122:Protein Subunits; D017948:Retinal Rod Photoreceptor Cells / Q000737:chemistry; D014981:Xenopus
chemical_list: D002147:Calmodulin; D054815:Cyclic Nucleotide-Gated Cation Channels; D007473:Ion Channels; D021122:Protein Subunits; D002118:Calcium