title: hKCNMB3 and hKCNMB4, cloning and characterization of two members of the large-conductance calcium-activated potassium channel beta subunit family.
abstract: We cloned two beta subunits of large-conductance calcium-activated potassium (BK) channels, hKCNMB3 (BKbeta1) and hKCNMB4 (BKbeta4). Profiling mRNA expression showed that hKCNMB3 expression is enriched in testis and hKCNMB4 expression is very prominent in brain. We coexpressed BK channel alpha (BKalpha) and BKbeta4 subunits in vitro in CHO cells. We compared BKalpha/beta4 mediated currents with those of smooth muscle BKalpha/beta1 channels. BKbeta4 slowed activation kinetics more significantly, led to a steeper apparent calcium sensitivity, and shifted the voltage range of BK current activation to more negative potentials than BKbeta1. BKalpha/beta4 channels were not blocked by 100 nM charybdotoxin or iberiotoxin, and were activated by 17beta-estradiol.
authors.affiliation: Institut für Neurale Signalverarbeitung, ZMNH, Universität Hamburg, Martinistr. 52, D-20246, Hamburg, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Behrens
authors.forename: A
authors.initials: A
authors.lastname: Nolting
authors.forename: F
authors.initials: F
authors.lastname: Reimann
authors.forename: M
authors.initials: M
authors.lastname: Schwarz
authors.forename: R
authors.initials: R
authors.lastname: Waldschütz
authors.forename: O
authors.initials: O
authors.lastname: Pongs
mesh_terms: D000595:Amino Acid Sequence; D001923:Brain Chemistry; D002118:Calcium / Q000494:pharmacology; D018999:Charybdotoxin / Q000494:pharmacology; D003001:Cloning, Molecular; D004553:Electric Conductivity; D004958:Estradiol / Q000494:pharmacology; D006801:Humans; D051038:Large-Conductance Calcium-Activated Potassium Channel beta Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D009928:Organ Specificity; D010455:Peptides / Q000494:pharmacology; D015221:Potassium Channels / Q000737:chemistry / Q000187:drug effects / Q000235:genetics* / Q000502:physiology; D024681:Potassium Channels, Calcium-Activated; D012333:RNA, Messenger / Q000032:analysis; D016415:Sequence Alignment; D013116:Spinal Cord / Q000737:chemistry; D014018:Tissue Distribution
chemical_list: C403242:KCNMB3 protein, human; C410183:KCNMB4 protein, human; D051038:Large-Conductance Calcium-Activated Potassium Channel beta Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; D009419:Nerve Tissue Proteins; D010455:Peptides; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D012333:RNA, Messenger; D018999:Charybdotoxin; D004958:Estradiol; C064719:iberiotoxin; D002118:Calcium