title: An unconventional calmodulin-anchoring site within the AB module of Kv7.2 channels.
abstract: Calmodulin (CaM) binding to the AB module is crucial for multiple mechanisms governing the function of Kv7.2 (also known as KCNQ2) K(+) channel subunits, which mediate one of the main components of the non-inactivating K(+) M-current, a key controller of neuronal excitability. Structural analysis indicates that the CaM N-lobe engages with helix B, whereas the C-lobe anchors to the IQ site within helix A. Here, we report the identification of a new site between helices A and B that assists in CaM binding whose sequence is reminiscent of the TW helix within the CaM C-lobe anchoring site of SK2 K(+) channels (also known as KCNN2). Mutations that disrupt CaM binding within the TW site, helix B or helix A yield functional channels, whereas no function is observed when the TW site and helix A, or the TW site and helix B are mutated simultaneously. Our data indicate that the TW site is dispensable for function, contributes to the stabilization of the CaM-Kv7.2 complex and becomes essential when docking to either helix A or when helix B is perturbed.
authors.affiliation: Unidad de Biofísica, Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU, Universidad del País Vasco, Barrio Sarriena s/n, Leioa 48940, Spain.
authors.forename: Carolina
authors.initials: C
authors.lastname: Gomis-Perez
authors.affiliation: Unidad de Biofísica, Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU, Universidad del País Vasco, Barrio Sarriena s/n, Leioa 48940, Spain.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Alaimo
authors.affiliation: Unidad de Biofísica, Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU, Universidad del País Vasco, Barrio Sarriena s/n, Leioa 48940, Spain.
authors.forename: Juncal
authors.initials: J
authors.lastname: Fernandez-Orth
authors.affiliation: Unidad de Biofísica, Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU, Universidad del País Vasco, Barrio Sarriena s/n, Leioa 48940, Spain.
authors.forename: Araitz
authors.initials: A
authors.lastname: Alberdi
authors.affiliation: Unidad de Biofísica, Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU, Universidad del País Vasco, Barrio Sarriena s/n, Leioa 48940, Spain.
authors.forename: Paloma
authors.initials: P
authors.lastname: Aivar-Mateo
authors.affiliation: Unidad de Biofísica, Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU, Universidad del País Vasco, Barrio Sarriena s/n, Leioa 48940, Spain.
authors.forename: Ganeko
authors.initials: G
authors.lastname: Bernardo-Seisdedos
authors.affiliation: Unidad de Biofísica, Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU, Universidad del País Vasco, Barrio Sarriena s/n, Leioa 48940, Spain.
authors.forename: Covadonga
authors.initials: C
authors.lastname: Malo
authors.affiliation: Dept. Farmacología, UPV/EHU, Universidad del País Vasco, Barrio Sarriena s/n, Leioa 48940, Spain.
authors.forename: Pilar
authors.initials: P
authors.lastname: Areso
authors.affiliation: Molecular Physiology Laboratory, Departament de Bioquímica i Biologia Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Felipe
authors.affiliation: Unidad de Biofísica, Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU, Universidad del País Vasco, Barrio Sarriena s/n, Leioa 48940, Spain alvaro.villarroel@csic.es.
authors.forename: Alvaro
authors.initials: A
authors.lastname: Villarroel
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002118:Calcium / Q000737:chemistry / Q000378:metabolism*; D002147:Calmodulin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D051658:KCNQ2 Potassium Channel / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D062105:Molecular Docking Simulation; D009154:Mutation; D009474:Neurons / Q000378:metabolism; D011485:Protein Binding; D017433:Protein Structure, Secondary; D013329:Structure-Activity Relationship
chemical_list: D002147:Calmodulin; D051658:KCNQ2 Potassium Channel; C496914:KCNQ2 protein, human; D002118:Calcium
keywords: Calmodulin; KCNQ; M-current; PIP2; Signal transduction