title: The TRPV5/6 calcium channels contain multiple calmodulin binding sites with differential binding properties.
abstract: The epithelial Ca(2+) channels TRPV5/6 (transient receptor potential vanilloid 5/6) are thoroughly regulated in order to fine-tune the amount of Ca(2+) reabsorption. Calmodulin has been shown to be involved into calcium-dependent inactivation of TRPV5/6 channels by binding directly to the distal C-terminal fragment of the channels (de Groot et al. in Mol Cell Biol 31:2845-2853, 12). Here, we investigate this binding in detail and find significant differences between TRPV5 and TRPV6. We also identify and characterize in vitro four other CaM binding fragments of TRPV5/6, which likely are also involved in TRPV5/6 channel regulation. The five CaM binding sites display diversity in binding modes, binding stoichiometries and binding affinities, which may fine-tune the response of the channels to varying Ca(2+)-concentrations.
authors.affiliation: Department of Protein Biophysics, IMM, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands. n.kovalevskaya@science.ru.nl
authors.forename: Nadezda V
authors.initials: NV
authors.lastname: Kovalevskaya
authors.forename: Fedir M
authors.initials: FM
authors.lastname: Bokhovchuk
authors.forename: Geerten W
authors.initials: GW
authors.lastname: Vuister
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000737:chemistry; D015220:Calcium Channels / Q000737:chemistry*; D002147:Calmodulin / Q000737:chemistry*; D002462:Cell Membrane / Q000737:chemistry; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification; D011485:Protein Binding; D025941:Protein Interaction Mapping; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D050916:TRPV Cation Channels / Q000737:chemistry*; D013816:Thermodynamics; D014364:Tryptophan / Q000737:chemistry; D014982:Xenopus laevis / Q000235:genetics
chemical_list: D015220:Calcium Channels; D002147:Calmodulin; D010446:Peptide Fragments; D011994:Recombinant Proteins; D050916:TRPV Cation Channels; C492239:TRPV5 protein, human; C422827:TRPV6 protein, human; D014364:Tryptophan; D002118:Calcium